I just tried “which lacs have less than a 25% admissions rate” and it did a similar thing where it gave me a bit of a discussion and a list of colleges that it did not claim was comprehensive, but it said were included on that list. That list did include colleges outside the Northeast, like Pomona, HMC, CMC, Davidson, Grinnell, and Carleton.
“which lacs are little ivies” then returned an answer that said they were specifically in the Northeast and it also specifically referenced NESCAC.
Looking at the sources for that second output, and then just googling Little Ivies, it seems to me to the extent there is anyone pushing the Little Ivy concept these days, it is various for-profit college counseling websites/firms. It is interesting to ask why AI might be seeing these as notable sources, but maybe it is just a matter of who is putting a lot of easily usable content online in a way that helps an AI answer prompts like this.
But I would not personally assume that means in the real world, everyone is talking like that about LACs. I see that as people and firms with a financial interest in potential customers seeing LACs like that promoting that view.