I’ve not personally met someone like that either, but I AM terminally online and see it a lot. It’s usually Andrew Tate enjoyer types.

I’m in my 30’s and haven’t heard it out in the real world either, but that’s probably because the assortment of individuals who use females as a pejorative either don’t use it in public because it’s cringe and they know it, or because they don’t go outside.
That’s only my educated guess though.

When I worked in an FLGS I heard it from customers quite often, which we would always try to nudge them in another direction. It’s not the “country boys” who say it, it’s the 4chan/incel/Alpha-male set.