Teacherman...the knee is a hinge( back and forth). When the hips are rotated then you see the knee go parallel as a result( hinging). Emanski turns the hips and leaves the hands back and then hits. He is teaching hip /shoulder separation. His bat slot position he teaches will get the separation naturally later in his tapes and lessons
As for as cause and effect, you know who teaches scap load. If you have the correct arm and hands action then scap load is more natural. It is something I cannot force. When the bottom hand works under the top and the rear elbow elevates then the shoulder unit rotates more vertically then flattens...the scaps load if you want to call it that but not something that I can teach by itself