I think it makes pretty good sense from both of those perspectives.
It probably doesn't from the point of view that classifications should fit some neat content-description role, but that's never been the function that they actually serve except insofar as content descriptions have utility to the other purposes mentioned.
However, this thread started because many adult sci-fi and fantasy readers look down on YA books. That's the purpose for which I'd suggest that the distinction doesn't make much sense.
That said, Marissa Meyer's Lunar Chronicles (to pick a somewhat less known example) are pretty excellent sci-fi, if you can get past the annoying teenage romances of the protagonists.
Another good example of YA fantasy I've enjoyed that manages to dodge the trope: Diane Duane's Wizards series ("So you want to be a Wizard", "Deep Wizardry", "High Wizardry"), which seems to mostly stay away from typical teenager problems. The premise is not that novel, but in this case I found the execution quite satisfying, particularly in the second and third books. Without providing spoilers, I would note that the second book manages to avert one of the single most common tropes of YA fantasy novels (and of other series that avert it, most do so far later in a series). I'm also a big fan of "sufficiently descriptive language as magic" and "sufficiently analyzed magic", both of which these have quite a lot of.
(Note that I have not read the "updated" editions of these books that attempt to make some of the technology references less dated.)