If I'm not mistaken all the other "native" Youtube apps on other platforms are Google's own apps, and it's also their prerogative to choose the platforms they want to make native apps on. For example, they haven't made one for Roku either, and it's the #1 media streaming box right now.
So I don't see the problem here?
EDIT: One other thing. Google told them from the beginning that they'll only allow an HTML5 app. So what does Microsoft do? They make a native app - again. And then Microsoft releases the native app to their store, without Google's approval, even though they were supposedly "collaborating" on this, and then seeds press releases to the media that Google-the-bad-guy blocked them "again" - like it was "completely unexpected" or something.