Good point about the additional rotations. The shoulders actually rotate 3 ways. Somersault, and shoulder over shoulder, and then around the axis.
Just one of the complexities. There are two questions, what are the motions and the key positions--how do players recreate them. My own views are that if the stance, leg action, toss, and upward arm action are correct, the shoulders will tend to take care of themselves. With video you can compare the 3 types of rotation to good models and then try to figure out how to push your motion toward that.