I'm guessing that you think the hands weren't/aren't used in the below gif(correct me if I'm wrong)
It does make for an interesting discussion. Do the hands move in order to deliver the barrel? Or are the hands moved by other actions? I don't think anyone debates that the scap (and the muscles associated with it) are used in the process. But I also believe the hands play an important role in the process. Some may argue that the hand movement in the Pujols video is controlled predominantly by the scap or serratus anterior. While I don't deny that is part of what is happening, I also believe that Pujols is starting to set direction at this point (not complete by any means, but starting...). That process requires the use of muscles outside of the scap area as well. To me it is all a matter of what body part you want to focus on.