The 'push' that CY is describing occurs during the shift into heel plant ... during the uncoiling of the rear leg.
I understand, but like I said, I don't see any evidence of it. At the time of the shift into heel plant the rear knee is turning in and the thigh is pulling the lower leg. This causes the rear foot to come up heel first, then onto the toe. The evidence to support this is that the knee is bending, not straightening, and the rear foot is not flexing.
I think you may be confusing the pressure felt in the rear foot that the hips use for resistance to begin rotation, for a push. The problem with telling girls to push with the rear leg/foot is that if they do, they will push the entire body forward and end up with their weight 'over' the front leg instead of against it.