Re: the bolded - that's exactly it. Some people notice it, some don't. I'm no pro reviewer, but were I to write a piece on the Air 2, I, too, would have neglected to mention anything about vibration. Because I never noticed it until I read all the comments here. Maybe my fingers aren't sensitive enough, I don't know, but I had the thing for a week and used it heavily without thinking twice about vibrations.
Now, having read those comments, I think I know what folks are referring to. Still doesn't bother me in the least, and I've certainly never experienced any numbness/tingling - but I get that some people are very bothered by this. My guess is that these people are in the minority, which, perhaps, is why reviews aren't generally mentioning this. The reviewers represent the majority who (like me) don't notice it.
Just a guess.
That said, given the fact that people are talking about it, seems like a current review should at least address the subject.