My understanding is that any rotary movements in PMTS is the result of lateral tipping movements at the ankle, there is no leg pointing or steering. The action of inversion and eversion occurs at the ankle joint of the foot. The action of inversion at the ankle joint enables tipping of the inside foot to the LTE. The process of inversion of the inside foot helps to move the CM into the new turn and increase edge engagement and angles. I focus on tipping my foot to start this movement, but I do feel that the boots are rigid and does limit my ankle movement somewhat. I got into a discussion on another site about tipping and most did not agree it happens at the ankles.
My response " I edge by focusing on my foot and ankle at the base of the kinetic chain. Since everything is connected together tipping the foot will cause the knee to also tip and move. A force acting on the foot will travel up through the kinetic chain move to the leg, thight and even to the hip. However by focusing on the foot you have much better fine control over you edge angles that at your knees. Next time you are on the slope with your boots no more than hip width apart, and you want to turn to the right only focus on the right foot, tip the foot the the little toe edge at the same time lighten the foot while flexing the right leg as you start to turn. Keep tipping and flexing that foot and leg while gently allowing the outside leg to lenghten stay balanced on the outside leg, you will make a nice turn to the right".
His response
"I have actually tried that several times, in fact, and it doesn't make any difference in a turn. I can see where some skiers might think that they are turning with their ankles but, in reality, they are actually turning with their knees because their ankle is laterally immobilized by their boots. When somebody can show me how they edge their skis by moving their ankles without moving their knees, I will be a believer. Until then, not so much"