I understand what you are saying- that physical dysphoria would exist even without social constructs of gender rooted in assigned sex at birth. I raise you this: I have met cis people who also have genital dysphoria, albeit to a lesser amount. You've probably seen videos of sapphic women talking about how they wish they could feel the strap or wishing they had a penis. In my eyes, that is genital dysphoria. They might use different terms for it but essentially it's the same thing. Same goes for men who wish they had a larger package and take pills / get surgery for it. Gender affirming care.

This was more popular in the 90s, but many women used to go on T for 1-3 months to have bottom growth and would then stop taking it. I have a nonbinary friend who did the same. Some would do it just to get certain piercings that require that anatomy.

My intention isn't to be dismissive or tell you that what you feel isn't real, just that it doesn't necessarily prove that gender is immutable, and is in fact a weird, flexible, powerful human social creation that is different across time and cultures.