Unlike you I have my students concentrate on back foot and back knee drive as the initiation of hip rotation. If you lift and turn your back foot the hips must rotate. I find that the students that concentrate on the hips rotating have more problems with spinning out with both hips and shoulders.
If the back leg starts hip rotation then the front shoulder can be in control when it pulls back. If the hips rotate too much either too soon or too much the front shoulder is now more suseptable to flying open as opposed to pulling back.
Big point on all of this is that back foot drive (lifting or dragging) allows the front shoulder to remained in a controlled rotation (creates x factor stretch) however bug squishing of the back foot forces the front shoulder open imidiately with back foot rotation. This is caused by two forces at working together forcing the front shoulder to open. The back knee internally rotates with weight transfering rearward which at the same time due to rearward weight transfer forces the front leg to straighten early in the swing.
Any thoughts on this. <<<
I find that as hip rotation is being initiated, both knees (front and back) start to rotate. Although I did not prefer it, I see little problem with rotating the back-knee to initiate hip rotation. I teach my students to land on the ball of their lead-foot in a closed position. Then rotate the foot open about 45 degrees (like Pujols) at heel-plant to initiate hip rotation.
I do differ with you on the role of the lead-leg. You state, "The back knee internally rotates with weight transfering rearward which at the same time due to rearward weight transfer forces the front leg to straighten early in the swing." -- I have read similar theories that the lead-leg is puled straight by hip rotation. These theories imply the lead-leg contributes little or nothing. Whereas, I contend that the extension of the lead-leg contributes more to hip rotation than the back-leg. The video below explains my thoughts on the role of the lead-leg.
Giambi - Momentum & lead leg