Nail, great posting but Im not quite following you. The confusing part for me is how you define "close/open hips". To me your joints eather open or close. If you bend your knees that is closing your knee joint. If you bend forward at the hip that is closing the hip. For instance retracting your knees up would cause your hips to close. Thats why I dont understand why you say that as you enter the float and flex your knees you open your hip at the same time.
Ancles also work differently. The only way you can flex your ancle joint would be to pressure the tongues of your boots with your shins. And that you can only do by moving your CoM forward and jamming your skis against the snow. The opposite of what we do during a float or a retraction transition. You can offcourse lift your toes upwards causing a flexing movement of the ancle but that will not be flexing your boots at all. Sort of the same of tipping your ancle inside the boot sideways. The boot is rigid enough to withstand such subtle movement. Same applies to the effort of flexing our ancle joint by trying to lift the front part of our foot uppwards.
Look at the following pickture. I tried to draw your stance from the side in the different frames. Frame 3.5 is missing from the photo montage but this is where you experiance the most impact from the bump.
1 - 2
Ancles: remained the same or closing a small bit
Pressure: increased due to snow contact
2 - 3
Pressure: increased due to turn forces
3 - 3,5
Pressure: increased due to bump impact
3,5 - 4
Pressure: no pressure
4 - 5
Ancles: remained the same
Pressure: no pressure
As we can see from this diagram and these frozen frames the bump impact comes quite late in the turn. Nail has allready entered the turn transition as he hits the bump. On a regular groomer or if he had skied an easy zipper line there would never have been a bump impact and frame 3.5 would have not existed. The big difference I think is that as we start to flex while skiing the technical line is that we experiance compression during the flexing part of the turn. And the float is not the time from release to edge engagement in the high C. Insted the float starts at in frame 4/2 and stops in frame 1. And we extended through out the float. The opposite to skiing on a groomer.