If you were an actor and you wanted act the part of an aged person. Apart from the make up , and dress you would develope the walk that most aged people have. That is you would walk without lifting the heel of the standing foot from the floor. which in turn can make the head bent over and be too far forward. So if you don`t want to dance like an aged person learn at what point the heel leaves the floor of the standing leg and where the moving leg should be at that time. What happens with an aged person is after a while the muscles used in walking correctly stop working.If you don`t use it you lose it That is another advantage that dancing correctly has. Once a walk is learnt correctly I doubt if it will ever get lost.
"So if you don`t want to dance like an aged person learn at what point the heel leaves the floor of the standing leg and where the moving leg should be at that time."
Yes, however you have to realize that there are at least three different cases in dancing, each of which will have different timing.
First there is a walk - literally as described in the book - with no rise and no fall and the body at carried at a fairly normal altitude. In that case, the standing heel releases from the floor as the moving foot passes it.
Next there is the transition from step three of one figure into step 1 of the next. In this case, the footwork of the standing foot is not HT, but actually TH. And in this case, the standing heel will not rise until well after the moving foot has passed it.
Finally there is the case of a rising step, where the footwork is heel toe and an upswing is being generated. In this case, the standing heel must break free from the floor slighlty before the moving foot passes it.
Ultimately there are probably a few application specfic variations in between these major three. But the key lesson is that in addition to practicing the walk case which occurs literally in only a few places (and event those are generally executed lower in the legs with a different technique today), you must also learn to use the slightly different technique which is appropriate to the other situations encountered actual dancing.