I think there's nuance to conversation to be had about he/him lesbians and she/her gays. Being a he/him lesbian, or a she/her gay, is not the same thing as being a straight man/girl claiming to be a lesbian/gay. I think a lot of the confusion stems from the fact that gender is a complicated construct; both neurobiological and social.
When we say "guy" or "gal", we tend to apply it to queer peoples who socially are aligned more with a certain category. Like a genderqueer lesbian who uses masculine terms or adopts masculine roles, we can call that a guy; because guy is generally also used for social category beyond just "binary male".
Of course, there's also kneejerk reaction because of history. Trans women were attacked on the basis of being "autogynephiles", or like a "super-dedicated gay man"; so when we hear "she/her gay", especially older members of community - or those familiar with older history - tend to associate it with a time where trans women were a third category.
Similarly, for trans men; straight trans guys were often seen as "predatory lesbians seeking staright girls", and gay trans guys were often seen as "wannabe gay men/not serious about the male part" (because we think of gay men as half a man as that's how patriarchy treats them). So when people hear "he/him lesbian", especially straight trans guys, they assume that it's talking about them and go back to a time where "butch flight" was a conspiracy.
Ultimately pronouns isn't gender. Gender isn't fully social (rather, an internal perception of sex; i.e neurological and according to recent study genetic as well); but the language we use to talk of things associated with a gender/sex are social, and social rules are not set in stone. Logically queer people tend to agree, but we need to recognize that you still need to address internal bias - and having internal bias from growing up in a heteronormative society does not make you just like "those bigots".
Much like how sex has a bimodal distribution rather than binary, so does gender, and much like how we assume sex before the person has the language to describe themselves, the words are not concrete nor prescriptive.