I'm not saying they're right, but the Brewers Association seems to think there's a difference between a Quad and a BDSA.
Then there's the argument that the reason that the BJCP doesn't really draw a distinction between the two styles is because the BJCP is just for little 'ol homebrewing competitions, and it's really the Brewers Association that is more authoritative because the BA is used for real brewing competitions. Not my opinion, but I've seen it out there-