You write-: "Is it possible that the ulnar deviation is simply an effect, rather than a cause (club pulling the right wrist into ul. dev.)? I would think that with the momentum of the club moving at decent speed, it would be pretty difficult to prevent ul. dev. of the right wrist post impact."
That's how I think of the situation. I think of the right wrist's ulnar deviation action as being passive (reactive to other forces) rather than being active (due to active muscle contractile forces within the right upper limb).