I think Jack used it to catch Will off-guard and to see if he could gain an advantage - I'm pretty sure, for example, that Elizabeth would give him no quarter for fighting in the altogether, but Will probably would (even if he weren't immortally strong and fast).

As for big strong Will - yep, you got exactly what I was going for without saying too much out loud. *BG* I like some top!Will on occasion myself.

Thanks for feedbacking!