On a random note, I love that this theory got several likes, yet no one mentioned the fact that Xander's voiceovers were recorded no later than March-April last year, and the game Shovel Knight was released last June. I know the game was super-popular right out the gates, but I never saw a shred of Smash support until the ballot opened this year.
In any case, I think we're putting way too much stock in this whole thing. Obviously I assume Tamaki had more to go on than the false amiibo listing and upcoming YCG announcement, but until that's elaborated on, I'm taking this with a pillar of salt.