werewolves are starting enemies to be fair, they're not supposed to be stronger. they're pups playing with you.
another story is Miniatures who's a bull woman and you don't want to grapple her if you're not very strong
as for grappling fails, well, you're punished with being damaged after you end the grappling, plus stamina losses. not exactly sex. you get fucked, though, if you initiate wrestling, but then let them break free. you end up lying face down and it basically is the same as losing the grappling, but you can stand up though