That reminds me, I still have to put up the explanation at oneoftheonly.com for why this phrase doesn't make sense and is the new "could care less".
Definition 3 from Merriam-Webster[1] of "only": FEW
I can say "one of the few", or "one of the only", and they both make perfect sense (and have the same meaning). You're being blindly prescriptive without even doing the legwork.
For example: Alaska and Hawaii are the only non-contiguous U.S. states. Alaska is one of the only non-contiguous states.
The 'only' is part of the group definition, implying the individual 'one' is part of a small subset of some sort.
This is in contrast to people mistaking one word for another.
In fact it's even more vacuous ("nothingburger") because sometimes it's not even clear which way the person means it; if I say "I'm one of the only people to do a handstand on a Thursday morning", do I imagine that I'm in a large group or a small one?
[Edit: this paragraph added to respond to post below saying I'm not going to win, which was edited out and I couldn't respond to for some reason.] I'm not trying to "win" any more than I would try to tell people that literally isn't a synonym for figuratively; I know that ship has sailed. That doesn't mean I'm not allowed to say it doesn't make sense, and I'm very aware that people get extremely angry about it for some reason, as if it's a personal affront. Not everyone has to buy into the cargo cult of descriptivism (particularly in the face of absurdity), differences of opinion are still allowed :)
(edit - for the record, this was in response to the first paragraph only, as the others were edited in afterwards)
The grains of sand example should make it clear: it is not true that this grain is one of few at the beach, but it is true that it's one of the only. This makes it a poor expression for scarcity, and while obviously we know what was actually intended (as with "could care less"), that doesn't really make it any better.
FYI for anyone reading this (not directed at you specifically): the 'delay' option in profile setting adds a delay before your comments appear publicly, giving you a buffer for edits and deletions before it goes out to the world.
Personally it helps a lot with ensuring I'm happy with the comments I make, and it helps avoid situations like this where multiple layers of retroactive changes make the conversation hard to follow.
Also it's difficult not to call out the hypocrisy of descriptivists simultaneously saying that basically anything goes, but my preferred use of language in particular is wrong and I need to listen to what they prescribe :P
BTW thanks for the hot tip regarding the posting delay feature! Lord knows I need it, nothing induces https://en.wikipedia.org/wiki/L%27esprit_de_l%27escalier like hitting that reply button :"D