When a player "vertically stacks" at setup he takes virtually all tension out. When he goes to load, he does put tension in the stance prior to hitting. Even if the hitter sets up without vertically stacking, but with any bend in the knees, there has to be tension. As far as the upper body, the hands are generally loose until the bat is initiated.
Have you ever seen a boxer that is totally tense and tight. He cannot fire the punches in. He starts loose, weave bob talk weave get things in motion then POW! Try to throw a punch totally tense to start. However, try to throw a punch without tensing at all. Cannot happen. I think you guys are all correct.
However, BlueDog is criptically right. You are tense at load, just like a boxer. However, as a hitter you start loose.
I heard Cruk say that he went to load when the pitcher went to load. " I showed him my hip pocket, when he showed me his." No he did not. He went to load when the pitcher landed. And I'm sorry the backside rotation does not lead the swing, I CAN prove that. The hands lead the swing or it is simultaneous, no exceptions.