I’m sorry, but I this just isn’t true. Calling women females is definitely an incel thing (although admittedly has come more into mainstream (male) lexicon because of the algorithms).

Female/male is an adjective. Woman/man is a noun. A woman is female (not in a TERF way, lol), but she isn’t a female any more than she is a short.

While I’ve not done a deep dive into the origins, incels pushed the female thing it seems largely because they don’t see women as human and want to make them sound like they’re a different species. It might have even started off from incels calling women “the female species” because that’s a term I’ve definitely seen before in those communities.