"If you release your toe prior to lowering your heel, you will have momentarily lost contact, in effect picking up and placing the foot."
I would dispute that. Provided you aren't depending on the moving foot for slowing friction or partial weight support, "Picking up and placing" would be distinguished by a rise of the net mass of the foot. Simply rotating it from a toe down position to a heel down one would not constitute raising the foot, even though there would be a moment when no part of the foot was in contact with the floor. Indeed, for moderate heel heights, the center of mass of the foot may actually descend, since the tip of the heel is closer to ankle than the tip of the toe is.
"I should also mention that since it isn't natural to flatten the foot when it is in advance of the body, an unusual feature of this action following a Whisk or Curved Feather is the movement of the body *before* the foot. That is to say, for a very brief moment, when the body first starts to move, the toe stays fixed in its position, for just enough time to allow the body to arrive in a natural position over the foot. It's a very subtle detail, but one that makes all the difference between a skimming heel lead that's natural, and one that's forced."
Indeed - but this detail is one that should not be unique to these circumstances, but instead present in every step 1 action. It may be associated with promenade and outside partner positions because they make the fault of its omission more obvious, but it is really the fundamental technique of a lowered forward action - the body moves first, and brings the foot.
