DING DING DING!! You and Sidewinder agree on something. And it is an important point.
You are already starting your throw, or turning, SOONER than Paige. Paige is waiting a split second and building the whip before accelerating her arm. She is WAITING to throw.
BTW, what helped me the most was not worrying about all the footwork, rotating or planting, but WAITING. Waiting to throw until after my disc had reached my face then gripping the disc as tight as possible and throwing as fast as possible. If you start throwing while your arm is back, you are losing the benefit of the whip and the power you generate from your "awesome" hip turn.
Just do whatever you are currently doing for whatever reasons, but WAIT to throw and then explode very fast.
Also, your forward shoulder is strangely collapsed or hinged. Paige's shoulders are on the exact same plane as her forearm AND her disc. Your disc and forearm are on a different angles from each other and all angles are different than your shoulders. I don't know how to fix that, but I imagine getting your arm and wrist at same angle is bound to help. Does your disc sometimes flutter when you throw "hard"?