Don't forget that Apple has officially taken a liking to him, and that he is getting unusual access for a "regular guy". Pre-release hardware to review, invitations to private Apple media events, etc.
It would be in his best interest to not anger Apple or they instantly cut off his access. See: Walt Mossberg.
This is what all of the industry do. If you review graphics cards and you put out a negative review, no more pre-release graphics cards for you.
But Gruber's significant articles (like this one) are based on information that is public available. Most people just sees a chair, they don't see the thinking behind the chair.
What Gruber does best is to explain how Apple thinks, I know of no journalists that comes anywhere close to understanding Apple.
I agree that he probably understands the motivations and spirit of Apple better than most. My point is that he's now a part of the system in a subtle way, and to think about it when reading his coverage. He's no longer just a guy with a blog.
Andy Ihnatko is less of a fanboy, and still quite insightful about Apple. He has a very good natural sense of which rumors are probably true. And he's much funnier.
It would be in his best interest to not anger Apple or they instantly cut off his access. See: Walt Mossberg.