Points taken. But it seems to be a general piece of advice for anybody not to 'round' the shoulders but keep them back and down and the scapula flat against the ribs. I'm trying to understand why it's problematic to have the scapula in any other position. After all, any time you move the arm beyond a certain point the scapula naturally moves to accommodate that range of movement. I'd have thought that artificially holding it down would more likely cause tension in the arm because you're forcing it to the limit of its range in the joint.

Is it just a problem of tension in the muscles that hold the scapula if it's not in the right place? Or does it affect its joint with the collarbone to have the scapula rolled forward for instance? I think I've read that somewhere.