Troons constantly piggy back off of gay rights because most people are okay with the gays nowadays and they want you to think it's just "the new gay" and that you'll be "on the wrong side of history" if you don't let a bunch of middle aged men with sissy fetishes into your preteen daughter's locker room.
Everyone has a sexual orientation, that is an attraction to either the opposite or same sex (or both), so the "born this way" narrative is pretty compelling and easy to understand-- if you're a straight guy, you can think "well I wouldn't be able to force myself to take dick so I guess lesbians would feel the same way".
"Gender identity" on the other hand is just a bunch of made up bullshit. Most of us recognize what we are born as, but we don't have some sort of mental situation feeling like we MUST adhere to stereotypes associated with the sex we were born as. They say stuff like "If you woke up one day in the opposite body, wouldn't you transition to get back to being your real 'gender identity'?" and "Wouldn't you be uncomfortable if everybody treated you like the opposite sex?" .
There are some people who would answer yes to this, moreso men than women, I think due to the social stigma against being "girly". But most people I've talked to, including nearly every single woman I've talked to about this, wouldn't care at all. If I woke up as the opposite sex, that would mean I was a member of the opposite sex. If everybody used the opposite sex pronouns for me, I wouldn't care because that doesn't change what I really am.
There is no "cis" analogous to "straight". If we have to make an analogy, it's more like "non anorexic" (I recognize my body as the weight it actually is) or "non schizophrenic" (I don't hear imaginary voices). Recognizing reality is nothing like having a sexual orientation.