Your example contradicts the claim. They say "assigned male at birth" rather than "male", because they believe you can be a female even if you were assigned male at birth.
It's more that male/female is not a single binary, it's several bimodal spectra. Chromosomes of xx or xy don't perfectly line up with birth genitals, birth genitals don't perfectly line up with endogenous hormones, and endogenous hormones don't perfectly line up with internal sense of self, several of those things can be changed later, and none of them are clear binaries.
Not even 99.98% of people have unambiguous genitalia (it's about 99.5-99.97% [1]), before we even get to people with the "opposite" genitalia of what their chromosomes would suggest. An in any case, genitalia was only one of the 4 things I mentioned, and are also one of the ones that can be changed later.
Trans bottom surgery has one of the highest satisfaction rates of any surgery. You're entitled to your opinion, but I'll rely on the opinions of people actually living with the surgical results. This [1] lists a 94-100% satisfaction rate, which to me feels a fair bit higher than one might normally expect from victims of "mutilation".
> Your example contradicts the claim. They say "assigned male at birth" rather than "male", because they believe you can be a female even if you were assigned male at birth.
I'm not sure that's a contradiction so much as it's trying to weave through people's own synonymizing of the two terms where a distinction is being made. I hear your point though.