I'm having trouble with this. I just don't have lateral ankle movement in my boots. I can tip my boots left and right, and I can flex the boot forward. That's it. I can change my body position over my boot. I have a molded footbed, a molded boot tongue, and molded liner. The liner is the consistency of a pencil eraser - movement is very small. My boots are built to eliminate interior movement, not to utilize it. Pronation and supination have no relevance.
And while whatever fancy dancing you guys are doing inside your boot in all that extra room you have, you still have to move the boot to move the ski. Laterally, the calf has to move. Has to. Fore and aft, it's all the ankle joint. Both are assisted by upper body position.
So it's ski position we move to - move to an edge angle, move fore aft to affect position/pressure. (We also rotate, but that happens without motion of the foot inside the boot). To me, big toe/little toe, ankle subtleties, all those dozens of little bones and joints - is in the balance category.