These statements are a bit of a fallacy though. What's a core gamer? Someone who plays everyday? Someone who owns all the systems? Personally I don't consider the person who plays just-one-game a hard core gamer. People who only play Call of Duty, or just FPSes, or only RPGs and MMOs like WoW. But that's just my interpretation.
And in that group you have some people who might play Dance Central everyday and consider the Kinect hard core. They may have been aiming at the same "casual" market Wii went for with motion controls but there's lots of people who slide in and out of that category. My boss PC games but he got a Wii for his kids. He'd buy Kinect but doesn't see a need to now. My other work colleague plays Halo games and basically the Lego games. Occassionally trying something different (if I sell him on it). But he only plays once a week, if that. He got a Kinect because he got a good deal.
Also there are only so many first party and second-party exclusive Xbox games, and most of those are "hard core" games, and their Kinect games are casual. But the third party games for Kinect are always casual. So it's not just Microsoft who thinks Kinect = Casual.
To me the Kinect fails it's core principal. The idea is that motion controls should be so intuitive that virtually anyone can play a Kinect game without thinking about how to do it. Unlike controller games that are only a little less complicated than driving a car. The lack of responsiveness in Kinect seems to make most experiences with it somewhat baffling and non-intuitive.
And what do you expect a company rep to say about their product? If you were involved with something that was a bit crap and your reputation was tied to it are you going to go around apologising? It doesn't work, ask Brad Pitt about Meet Joe Black.