Homosexuality doesn’t involve claiming to be something you’re not, though. “Transgender” requires both a concept of “gender” (as distinct from sex), and also the idea that the body can or should be changed to fit into the metaphysical concept of “gender”. Whereas until recently people really only believed in sex, as a material fact. If you fervently wished to be the opposite sex, this was taken as an indication of homosexuality, or just not fitting into social convention.
Yes, I defo feel like the sticking point for trans ideology is the fact that humans can't change sex. So in material terms they're not women as they claim, which undermines their credibility for many.
However, it's not impossible that both homosexuality and transgenderism arise from a developmental condition that subverts the standard impulses usually observed in that sex. The homosexual man feels the sexual orientation of a woman and the transgender man feels orientated to women in other ways.
The studies that have found transwomen to have brains more similar to women than other men do (even accounting for the diversity between individuals of both sexes) possibly support this hypothesis.
They could both feel more aligned with the opposite sex for developmental reasons and it's just a physicality that prevents the TW from manifesting their 'femininity' because they want to change sex rather than just embrace a female sexuality. But the physicality of a male body doesn't necessarily negate a cognitive makeup which is somewhat closer to women than the typical man's brain is. .
In effect the TW identifies as a woman whilst the homosexual man just acts in a feminine manner and manifests a feminine sexuality. Like how one person may identify as a cat whilst the other just walks around on all fours and meows.
I'd find it less confounding if homosexual individuals acted exactly the same as other members of their sex aside from their choice of sexual partners but they don't. Lesbians often have masculine haircuts, dress in a masculine fashion, and have butch demeanors whilst gay men often have camp mannerisms and gravitate towards female friend groups, etc etc.
Apologies if it sounds like I'm casually debating the lived experience of gay people/being insensitive. I'm just trying to view it through the same lens we use to examine trans ideology