This random article I stumbled across while looking myself takes Gruber's assumptions as fact, which I believe to be Apple's intention.
"The company is also changing the way it handles press events, according to worldwide marketing VP Phil Schiller. While Schiller has refused to go into any more detail, Daring Fireball's John Gruber notes that last week, he and others in the media were given separate, solo product briefings on Mountain Lion." http://www.macnn.com/articles/12/02/16/os.x.updates.to.becom...
Gruber actually wrote, "I'm guessing" because he didn't have the sense, integrity, or care to ask "Hey guys, how many other people will you be giving this personal, private, ego-stroking presentation to?"