You dont have a technique book have you. I'm not sure I understand. If the body is in place before the step that is not CBM it is CBMP and that we don't want on this step do we.
Again if you look at the chart you will see the two foot positions. One as the step is taken and also showing the turn over the same foot.
Whilst I have your attention I would like you to look at the first step in the Waltz on a Natural And the first step in the Foxtrot. Apart from the alignment where is there any difference.

"I'm not sure I understand. If the body is in place before the step that is not CBM it is CBMP and that we don't want on this step do we."

You don't understand because you misquote!

No one said the "body is in place before the step", what was said is that the CBM rotation occurs before the foot is placed.

"you look at the chart you will see the two foot positions. One as the step is taken and also showing the turn over the same foot."

The chart shows you only the feet. It does not show the body orientation. The body rotates somehwat during the CBM, then holds that still largely forwards direction until it arrives over the position of the SECOND step, which is to say the LEFT foot. Only then does it complete the rotation.

There is rotation of the body before it arrives over the right foot on step one, and as it arrives over the left foot on step two - but there had better not be any rotation of the body when it is over the RIGHT foot.

"Whilst I have your attention I would like you to look at the first step in the Waltz on a Natural And the first step in the Foxtrot. Apart from the alignment where is there any difference."

The primary difference is that the right knee relaxes more on arrival on the waltz, to absorb some of the arrival geometray and create the more underhanded path of waltz rise. In contrast for the foxtrot the right leg remains relatively straight, contributing to the early completion of foxtrot rise, and most importantly, leading the "stand up and close" of the lady's heel turn. Soft knee - waltz turn. Braced knee (Moore's word, perhaps a bit too strong as it should not be interpreted as locked) - foxtrot heel turn.

I am not the least bit concerned about what happens after the step. The matter under discusion is the first step. They are the same.
Another intersting point was one of the pupils brought their Laptop with them and freeze framed the couple from a IDSF competition at the point where they were both fully extended to the toe both front and back. Then asked which way are they going, is it forward for the lady or is it forward for the man. One smart person came up with the answer only by looking at how a piece of chiffon appeared to be billowing. Otherwise there was no other clue. Interesting isn't it.

"I am not the least bit concerned about what happens after the step. The matter under discusion is the first step. They are the same."

You can only call the steps the same if you are content to IGNORE the rather obvious fact that they end with the body in different positions. They must, because their function is to set up for DIFFERENT types of following actions.

Not caring what comes next proves only your own IGNORANCE. You won't even begin to understand the steps at all, until your consider that their primary role is precisely to set up FOR WHAT COMES NEXT.

I think your whole trouble is that you don't beleive there is a mid point ( split weight. That at the full extent of the stride you are on the heel of the front foot and the toe of the back foot. It doesn't matter if it is Waltz with a turn or Foxtrot a simple look at a video will prove. If you are one of those who turns into a step and not at the end, you have built your castle on sandy ground. Like painting a piece of wood. Use the wrong paint for the priming coat and everything that goes on after is a failure.
Pinned up on the wall.
Tell me and I will surely forget.
Show me and I might remember
But make me do it and I will certainly
understand.

"I think your whole trouble is that you don't beleive there is a mid point ( split weight. That at the full extent of the stride you are on the heel of the front foot and the toe of the back foot. "

Usually their is ISN'T any such situation. Sure, you see both feet on the floor, but you can easily tell that only one of them has weight at a time. Usually you'd be hard pressed to find even a single frame in a video where you could even make an argument that the weight might be divided.

Those who maintain the false belief that the weight is divided in actual dancing can be readily observed to be failing to commit their body to the movement - they hold it stationary while reaching their moving foot out, which is just all wrong in any dance but tango (and even there, it should only happen to a limited degree at the start of an action)

"If you are one of those who turns into a step and not at the end"

If you had a mature understanding of the concepct of "turn" in ballroom dancing, you would understand that some parts of the turn occur BEFORE the first step, and others occur only upon arrival on the second - but very little occurs in between.

Remeber, you have many SEPERATE variables: Body alignment, foot alignment, direction of movement across the floor - each has times during the overall "turn" when it is changing, and times when it is not changing, despite one of the other variables being in the process of change.

I suppose this gets a little scientific. There has to be a point where the weight is equally balanced, when it is just as far to the front as it is to the rear. A clock. The big hand goes from 12 to 6. It has to pass 3. which is split weight, an equall amount each way.
Another one that usually starts an argument is. The weight is never over the heels. I was told that once. Then I asked how do I go from one step to the next without the weight at some point being over the heel. Its not possible.
To get back to split weight, or equally divided as our technique books say. To do this and have an equall amount of weight over each foot. Here it is. Both feet must be on the floor. Which goes straight back to that other discussion which was lifting the foot off the floor, no contact. Does that make sense or does it not.

"I suppose this gets a little scientific. There has to be a point where the weight is equally balanced, when it is just as far to the front as it is to the rear."

Only as long as you nievely assume that the weight is always supported by the feet.

If you actually look carefully, you will see that the body spends a lot of time outside the footprint of what is at that point in time the only supporting foot. During this time, the body is receiving some support, but it is also in the process of "falling over" (however, usually without leaning or pitching).

It is no great stretch to go from partially falling in those numerous, lengthy off-balance periods to contemplate that during the so-called weight transfer, it is entirely possible that there's a point at which, briefly, neither foot is supporting the body.

It's quite obvious that this occurs in the quickstep... in the other dances, depends on who you ask, and perhaps who they are looking at.

One thing of which we can easily assure ourselves though is that any period of split weight is limited to the frame (2 maximum) of video where both feet are arguably stationary.

"Both feet must be on the floor."

Indeed, that is a precondition. But the precondition you miss is that both feet must be STATIONARY on the floor before split weight becomes possible (otherwise you are sliding a weighted foot, perhaps popular amongst retirment age social dancers but unheard of amongst trained ballroom dancers.

"Which goes straight back to that other discussion which was lifting the foot off the floor, no contact. Does that make sense or does it not."

It makes sense, but since you can't weight a moving foot without doing something very odd and dispruptive, split weight is equally unlikely regardless if the moving foot is actually on the floor or slightly above it - it is still a moving foot and not a standing foot. The presence or abscence of floor contact would only matter if you tried to make it a second standing foot. So you argument only concerns preserving an ability to do something THAT YOU SHOULD NOT BE DOING ANYWAY.

A clock. The big hand goes from 12 to 6. It has to pass 3. which is split weight, an equall amount each way.
Another one that usually starts an argument is. The weight is never over the heels. I was told that once. Then I asked how do I go from one step to the next without the weight at some point being over the heel. Its not possible.
To get back to split weight, or equally divided as our technique books say. To do this and have an equall amount of weight over each foot. Here it is. Both feet must be on the floor. Which goes straight back to that other discussion which was lifting the foot off the floor, no contact. Does that make sense or does it not.