LOL...well, I got the impression that Sean was just using his own colorful metaphor as a casual quip.

If another guy takes me aside and says, "Bro, you need to zip up your fly" -- it's going to bring me a lot more comfort as far as fixing the problem...especially if my penis is somehow visible and getting ready to poke out, through my crotch. It's easier hearing it coming from him, because he has the same "equipment" as me.

Plus, I'd imagine that, for most women, it would feel downright AWKWARD for her to have to let a man know that he is accidentally unzipped...especially if she isn't married to him or related to him by blood.