There's a lot of ongoing confusion for some posts resulting from overlooking the difference between the situations of actions described in a textbook, and the different situations that actually occur in real dancing today.
Consider the walking action for the standing dances. What is described is a flat action, done with no rise or fall, and at a relaxed altitude just a little below normal stnading height. It is of immense value for introducing many concepts of movement technique, but taken literally, it does not represent a situation which occurs in modern dancing.
Instead, we have different situations. As in pervious years, we have walk-like actions modified by rise and fall. Even in the era of the classic authors, these had different sequences of action from the flat walk. However, today they are even more different, as today we bend out knees to lower far more than in the classic era. Todays dancers start their descent much earlier, often from the start of step 3, and end it much later - no earlier than a quarter of the way into step 1, or nearly half way for some schools of though. As a result, one of the changes is that when lowering their foot will go flat sooner. In the old days, having the foot flat meant the lowering was nearly complete, because most of the rise and fall was in the feet. But today, most of it is in the legs - the few inches in the feet are just the beginning. So during lowering, we lower our foot fairly quickly, long before the feet pass, and then continue with the bulk of the lowering in the legs during and after the passage of the feet.
There are of course a few cases where a flat walk does occur in real dancing. For example, step 4 of a feather when followed by a three step. Or step 5 of a chasse when followed by a reverse figure. In the classic era, these would have been danced much as described in the book. But that is no longer approriate today. Because these walks occur between a lowering action and a rising one, their altitude is determined by the depth of the lowering. Today's dance lowers further into the feet, and so will dance through this flat walk at a much lower constant altitude than the constant altitude envisioned by the classic authors. It is now a different sort of action, and a result it requires different technique. When we are lower in our legs, with knees more bent throughout, our feet will spend more time flat on the floor than was appropriate in the decades when we danced higher, over comparatively straighter legs.