I don't think cleaning a barbecue grill is about sanitation so much as removing the built up, burnt crap. Heat will take care of the former; the latter could insulate the grill (so your food doesn't cook as evenly) or give an unpleasant flavor.
It also depends on the type of grill. Many common gas grills have thick bars with a grease channel, which would trap more gunk than thin rods common on charcoal grills.
