One of the things I don't understand, is that he's acting like the pinion gear and bearings only get lubed by what the ring gear slings around. Isn't the pinion low enough to get it's own lube? Especially when it's overfilled.
Not quite, James post describes it well. Also you may want to think about when towing up hill when the pinion will be at a higher angle and may not be submerged. It is the port above the pinion barring that the ring slings oil into that provides the real lubrication