Many people draw experience from the forehand hip rotation. In the forehand, the hip rotation is from the Right Leg to the Leg leg. So when they work on the backhand, they would assume that the hip rotation is from Left Leg to Right Leg. But the REAL MOTION is just hip rotation around the RIGHT LEG. This is the most important aspect of backhand, use the Right Leg as the axis and hip rotation around it. You will feel that the rotation is MUCH FASTER and MORE FRONTAL/ENGAING with the incoming ball. If you hip rotate from Left Leg to Right Leg, you WILL NOT HAVE ENOUGH TIME AND THE COORDINATION IS NOT AS EFFECTIVE. So hip rotate using the Right Leg as the axis and your movement will be more quicker and much more coordinated. You can see the Coach Guo is saying about the same thing. But he focuses more on "rocking". If you just use the Right Leg as axis to hip rotate, the effect is about the same.