There's a fatal flaw to the design. When folded up, the buttons and d-pad/analog nub are actually exposed on the bottom: they fold downward, becoming the bottom of the unit.
I highly doubt that's a fan-made mock-up. If I had to guess, I would say it's an official made-for-Nintendo mock-up for DS2 #19. They've probably got over 100 different possible configurations in-house at N right now for the DS2, and this one simply leaked to the net. That's my guess.