>>> Due to the muscular and skeletal structure of the shoulders they rotate exactly at the same time. You can not rotate onl with out the other. This is phsyically impossible. Try to shrug one shoulder without the other shoulder going the other direction or turn one shoulder without the other turning. You can shrug both shoulders together because this is a balanced movement on both sides of the spine.
Shoulders operate as one unit that is connected through the spine as the center point. <<<
This is one of those areas where we disagree. I have studied over a hundred overhead views of the best hitters. In every one of those swings, theirs lead-shoulder rotated 40 to 60 degrees independent of the back shoulder. In fact, in order for the hands to get back into a good launch position, the lead-shoulder will rotate (or shrug) inward 40 to 60 from its straightaway position while the back-shoulder remained fairly straightaway.
Below is a post I wrote on this topic and an overhead view of Pete Rose.
What about the shoulder shrug?
Overhead of Pete Rose