"Anonymous. Who said the shoulders keep moving and the centre does not. "
You did yourself, Don.
I quote:
"So once again. We lower and flex our knees , bend, recharge the knees, call it what you like. We lower vertically and not horizontally. Keep the shoulders moving. Never actually coming to a standstill."
What have you said here?
You stress that the lowering is vertical rather than horizontal, which means that the center cannot be moving. Yet you also emphasize that the shoulders should keep moving.
Do that and you will lean forward.
On the other hand, if you do it properly and move your center horizontally as you lower, there will be no leaning on top of your partner. But to do that, you would have to be willing to try sending your entire body forward of your standing foot, something you still refuse to contemplate.