The Mezzanine

What I'd expect to happen -- and what it sounds like this person was expecting -- is exactly the opposite: the hosts provide what is going on the grill, and drinks, usually; guests bring side dishes/salads/dessert.

Yep, same here, and my experience is from New Jersey.

It's more of a potluck thing - instead of only bringing what you yourself will eat, each person brings one dish for everyone.