he/him lesbians is largely a historical teem referring to lesbians in the 1980s scene who would identify as (typically butch) women but go by he/him pronouns (see stone butch blues)

(but it's old enough that some people have rediscovered it)

Unpopular opinion : once you start blurring the lines of what gender is, the straightness based definitions of things go out the window.

An FTM and MTF relationship is something alright. None of my business.

but, linguistically speaking, I don't think straight as a label applies to it, even though it's male + female.

it ties into the difference between someone being pansexual, and bisexual.