But regardless, according to the Tzitz Eliezer, once a person has the surgery, they are now considered the gender that they switched to, not the gender they were born as.
you talk about before and after the surgery but i don’t think it is clear that having the surgery is permissible. And that was heard from someone who had it.
Whether or not it is a longing, it is a nisayon. My close friend has a longing/craving/drive for something that is incessant but not permissible. There are ways to address that within the confines of halacha. Without taking the “poor me, I’m stuck because Gd dealt me a bad hand” path.