Why lie? Why cover empty boxes? They have enough goodwill and fanboyism without having to manufacture an aura. They curate it, no doubt. Which leads me to the hand-picked reporters. Calculated, definitely.
The reporters a risk? Nah. If Gruber yanked a cloth, he'd gain notoriety, be escorted out and others would glimpse something in a relatively similar form-factor or not at all (say, the iPad a year ago).
It would suck for Apple. But can you imagine the expectation over an iPad being revealed from a PR event went wrong? The expectation would be even higher.
There is little risk. They can manage. It seems like more work for Apple to lie at this juncture.