I will say, I was surprised that 2 different style of carbs rated at different CFM's right out of the box would run within a 100th of each other. That to me was more stunning than anything else from this test.
I think they probably try to make it run ootb with the type of engines they feel the buyers most likely won't tune for. My guess most of this carb sizing crap comes down to guy's not or poorly tuning.