And another question..........did he arch it for iron shots only?
Its a horizontal hand motion, but the opposite to the usual one, a reverse bend to the left wrist. A little bit of "insurance" against Throwaway and a closing clubface. Given a weak left hand grip you need to arch it to get the hands ahead at impact. You dont need to "turn it down" if you have a neutral to strong left hand grip.
Is the Arch a "compensation" then? Hmmm
D, are you saying you cant roll continuously and Horizontal Hinge? You saying the arch is a little hold off move to a roll? It could be.