I don’t actually know the answer, but I couldn’t resist digging at least just a little bit. My gut tells me that it’s probably related to rad fem in some way, like with gold star lesbians etc and that somehow trans people are involved.
The only thing I could really find was the term “bi lesbian” which is just a way to invalidate the identity of multiple groups of people at once.
I think maybe some people might be uncomfortable identifying as a label of lesbian, and there are other ways to express this, like wlw. Also for some, lesbian still carries a stigma or implies a connection to porn. Maybe that just means we should work on reclaiming it though, instead of shunning the label