>>141106554To answer your first question, gaming publicists talk out of their ass (not lie, per say, but there's lots of [CITATION NEEDED] going on) quite a lot, and as for what he actually gains from doing so, well, traffic, basically. Throwing something new into the rumour mill gets you into the spotlight.
Second, nothing's stopping him from refuting it in the same way that nothing is stopping anyone from refuting any Wii U rumours. And there might be an NDA or some shit - he might not want to go against Nintendo's wishes. After all, Ninty themselves are keeping wraps on the console's specs until E3.
There have been bullshit claims flying around everywhere coming from all sorts of people (some of them actually being gaming publicists like Geoff) and many of them have been contradictory and/or outright false. There is absolutely no reason to believe that this tweet holds any water as a matter of fact until we hear it again from the horse's mouth.