He left the DO lid off, and started with far more liquid (and various juicy bits) than might normally be the case for "baked beans." I can see how 300 for 2hrs wouldn't be wrong at all, here.
MY question is about the beans he started with. Unless you begin with raw beans that you soaked overnight, it all sorta looks over seasoned to me, because "baked beans" in a can from the store invariably already has a shitload of spices and even generic or tomato-based BBQ sauce of some kind mixed in, yeah?
That doesn't mean I wouldn't try his recipe, though!