A few things that stand out as suspicious to me:
-Apparachnid is 11 letters
-He specifically mentions that most of the game won't be in 3D. I know the demo was in 2D, but assumed that was so that off-screen footage won't look distorted. Why would they go through the trouble of using 3D models for everything unless they were going to take advantage of the 3DS's stereoscopic 3D?
-It's been stated several times how unlikely it is that we're getting two Eeveelutions. If we were, they would have both been shown in that short.
-The requirement to be surfing to evolve Inkay into Malimar seems crazy. It comes off as if this guy was trying to build off an earlier rumor, as if to say, "yeah, that's true, but what you don't know is..."
-No photos of the gameplay at all, just pics of the case, which can be faked, especially seeing as we have images of the box art online. Why describe the pokemon when you have the game and can easily show us? Unless you don't have the game.
-Also some other stuff that was apparently there before that was later removed, such as the guy claiming that he's the source of the PokeBeach leaks. It's already known that that's MageLeif, who had to sign an NDA, and stated that he wouldn't be leaking anything else.
Like I said, they're not all exactly smoking guns, but they do seem suspicious. Except that last one, if true that would definitely disprove the whole thing.