Yeah, you're on to something. I'd guess it's intense and precise coaching paired with people who don't do this sort of thing very often. It seemed to get a lot worse soon after they started trying to get a bunch more presenters involved, some years back. My guess is they didn't think the first couple of those were polished enough, so cranked up the prep, which, when applied to people who haven't developed outstanding presenter-talent, gives you a really fake and awkward effect. I think the somewhat rougher early ones were nicer, personally.
To their credit, I guess, most other events I've seen like this since everyone started trying to ape Apple's announcement style have the same problem, and usually worse.
They've been trending that way even at the live events. Last few years the obviousness of all the coaching and rehearsal has been extremely distracting. I mean it was there before but not quite so intensely. They all come off as robotic or like someone's holding a gun on them.
To their credit, I guess, most other events I've seen like this since everyone started trying to ape Apple's announcement style have the same problem, and usually worse.