Originally Posted by DropShotArtist
But if you keep the arm in line with torso as you said then the upper arm can't really be loose since if it was loose it would lag behind. And if it's not loose then there really is no transfer from torso to upper arm since it would be rotating as a unit with only the forearm and wrist lagging.
The upper arm would lag if shoulder is loose, which it really isn't.
There's nothing preventing energy transfer if upper arm doesn't lag, because a lot of that energy goes into external shoulder rotation in the forward swing rather than breaking the plane of the torso.