I'm not so sure that it is a hoax, consider that he went to all the trouble to take the casing off a game cartridge, print out a NDS label to put on the game similar to those on normal carts on the inside and then cover it up with a permanent marker and wait for someone to x-ray it or not. But then that does raise questions about his cousin having to return the game and then they would be suspicious as to why the game name was scribbled out (no pun intended
). In the even that he has dumped the game, his reasons for being traced may be valid seeing as the developers could check who they gave copies too and then further look into the leak, though that may be too much effort.
Either way it isn't long until the release of the game, as I see it if you don't play the "dumped demo" (If it even exists and you get your hands on it) and wait it will be a much more rewarding experience
.