M.Ted, I agree it's not about the sauce, I just think many N.Americans believe it is; at least, BBQ conversations in the US always seem to circle around the subject of sauces or marinades.

As for the slow cooking, I'll beg to differ. If it was about enclosed vessels and indirect heat, then there would be some sort of saucepan referred to as "the BBQ", and not the charcoal- or gas-burning contraptions we love to fight with.

No, I think (just an opinion, mind you) that the slow cooking before (or instead of) grilling on an open fire is a shortcut, a way around the problem, for those who find it difficult to cook on an open fire without burning the outside while leaving the inside raw (and let's face it, that's most of us). Me, I can do you a crisp-and-pink sausage in a flash. Literally :-)