I believe the idea with gender being immutable is that people who transition to another gender are doing so to align their gender with what they believe it shou

I believe the idea with gender being immutable is that people who transition to another gender are doing so to align their gender with what they believe it should be. In this way it is immutable; a person assigned male at birth, who later transitions to female, is no less female than someone assigned female at birth since neither truly chose to be female.