"However, once a student graduates to full bronze (figures 6 through 10), they ditch the foot closing, and move right on to foot passing Twinkles, of which there are several. It's a shame, because not enough time is spent on foot closing to make a lasting impression, and the student followers in particular suffer, because they typically have difficulty following any type of foot closing Twinkle, even when properly lead."
With figures such as natural and reverse turns, there often seems to be a progression for international style dancers such as:
1) Do foot closure figures in a stilted manner, with no flow
2) Develop flow in figures which lower with the feet apart, while often missing closure on the closing ones (for example stumbling past the initial natural turn in many competitive international waltzes).
3) Learn to do precise foot closure followed by re-establishing natural flow in the lowering.
That's in international style where a few foot closure lowerings do remain culturally mandatory at the highest levels, so dancers to continue to try to develop them.
One wonders with the closed twinkle if the reason it never gets a "stage 3" re-investment after developing the "stage 2" "hover telemark" twinkle is that it's simply unpopular... or if it's unpopular because it's fundamentally not a very good idea as a figure.
Generally speaking, the relative body and foot positions a partnership would be in on a rise while preparing to step in promenade is not the same as the relative positions they would have when lowered and moving strongly through the feet in promenade. Achieving a promenade (or promenade-able) position on the rise and then lowering vertically from that position would seem like it may require that either the risen position be somewhat loose, or the lowered position not be one from which the type of strong movement which advanced dancers would habitually seek can be taken.
Compare for example the close distance between the leading (men's left, lady's right) feet in the brush towards a continuity promenade to the substantially greater distance between those feet as the trailing leg comes through after a deep and traveling lowering in a continuity promenade. If the leading legs are not going to be able to reposition during the fall, one position or the other would have to be different from that used in the continuity case.