" If you have any trouble explaining this to your partner ask him how many times does he expect to lower on the same step."
Quickstep, any lowering can be broken into two pieces, regardless if you choose to think of it that way or not.
There is the lowering that occurs as your body moves over or is already over the foot. And then there there is the continued lowering that occurs as you bend your standing knee and project beyond the foot.
Technically, a lot of that second phase of lowering belongs to the next step. If you just continued down, you would be in trouble - but if you make sure that you have started up again as you begin to arrive on step one, you will be perfectly safe.
And there is no disagreement about this in the actual dancing of the world's best - only perhaps in how they describe it. If you look, the one point of disagreement is in the question of when you start up again - the English tend to hit their low point halfway between the positions of step three and step one, wheras the Italians tend to continue gently downwards until just before the body passes over the position of step one, and then rise more sharply.
And not that I spoke of the positions of steps 3 and 1. Almost all of this extra lowering is part of the duration of step 1, at least anything after the feet have passed would be.