I see. I suppose it sort of makes sense but it seems to imply that the skipper is using the jibsheet as a support (otherwise why couldn't he 'trap very aft' holding the mainsheet instead of the jibsheet) rather than a control.
I think the skipper should have the primary controls of the boat (main & tiller) to be better able to react quickly even if it means he can't trap quite as far aft (although I don't really see why not). If there is still a need for more weight aft, the crew should also move aft as much as possible.