The same usage occurs here in New England, and I've been told there is a culinary difference between "sauce" and "gravy", one having meat in it, the other not. This distinction only seems to be made on the East Coast, however.
I dunno. my grandma used to put all sorts of stuff, meatballs, chicken, lamb... but still called it sauce.
I keep my 2 feet on the ground, and my head in the twilight zone.