""The third step of the man's Feather Step is given as a TH in the technique books. Describe the exact positioning of the moving leg at the moment the Heel of the supporting leg should touch the floor. This type of question would throw light on the candidates understanding of the priciple of controlled lowering ". "
The correct answer for the examination is simple: whaveter the examiner is known to want to hear! And this will be known to the candidate, because you can't even schedule an exam without training by a recognized preperation teacher, who of course will know the answers expected by the locally available examiner.
As for the RIGHT answer: The heel will have to lower before the moving foot passes it. If it remained up until the moving foot was passing it, then the lowering would have to be abruptly vertical instead of the nice gradual diagonal, leisurely in both the horizontal and vertical direction, that we actually see on all of the best dancers.
Further, if someone is dancing with modern dynamics and making lots of usage of their knees, then the time at which the standing heel touches down is nowhere near the bottom of the lowering. In fact it isn't even to the halfway point of the lowering yet. The lowest point of the body will not of course be reached until somewhere beyond the position of the third foot placement, but the body would need to be more than halfway down as it passed over that foot. Otherwise you risk failing to ever get the heel down at all.
Some teachers will ask a student to dance for a while by arriving over the foot and only then lowering, but this is an EXERCISE and not the practice in actual dancing. The idea is that doing this will build strength in the foot - strength that would then (if the student reaches the point of being ready) be applied to extending the lowering in space as well as time. If someone tries to create the "real" action from day one, there is a very real risk that they will simply crash down without any control.
As for the lady, the backwards action there has basically the same timing as the forwards.
Incidentally, whatever Jonathan's "words" answer turns out to be, his "facts" answer is readily seen on his feather video. He gets that heel down before the moving foot has really moved much towards closing at all, and as a result generates a very nice lowering, that is controlled, artistic, and a great preperation for whatever would come next.