"That's doctor Evil. I didn't spend 8 years in evil medical school to be called mister, thank you very much."

De La Chappell syndrome, congenital adrenal hyperplasia, androgen exposure in utero, ovotesticular disorder of of sex development all result in a person with cis male characteristics and in some cases cis male typical genitalia despite having xx chromosomes

Gene expression is not as straightforward as people think. All sorts of weird shit can happen, and that's not even including gene mutations.

https://static.scientificamerican.com/sciam/assets/File/Pitch_sketch_final.png?w=2000

This is the best resource I've seen to show things relatively simply.

The TL;DR is that a whole "Y" chromosome isn't exactly responsible for "maleness", the SRY gene is. It's normally on the Y chromosome, but mutations can occur placing that gene onto the X chromosome. Inversely, someone could inherit a Y chromosome without that gene, in which case they would develop with female traits.

It's not considered trans because someone with 46XX plus the SRY gene would develop male genitalia, be identified as male at birth, and likely identify themselves as male. For some types of these conditions, there are plenty of people walking around with no clue that their chromosomes don't match their gender.

Disclaimer: I'm not a geneticist, so i could have explained something a little off.

I googled it for you.

https://en.wikipedia.org/wiki/XX_male_syndrome

In 90 percent of these individuals, the syndrome is caused by the Y chromosome's SRY gene, which triggers male reproductive development, being atypically included in the crossing over of genetic information that takes place between the pseudoautosomal regions of the X and Y chromosomes during meiosis in the father.[2][7] When the X with the SRY gene combines with a normal X from the mother during fertilization, the result is an XX genetic male. Less common are SRY-negative individuals, those who are genetically females, which can be caused by a mutation in an autosomal or X chromosomal gene.[2] The masculinization of XX males is variable.

Tbf, they kinda earned the right to brag.

True, but I do think it was warranted in this case.

Well you don't know people with PhD that don't tell you they have one

This is putting confirmation bias to the extreme.

Sometimes they don't tell you and just quietly update all of their usernames...

There's a bunch of them, but one more common example is Androgen Insensitivity Syndrome.

It's also possible to have a non-functional SRY (XY but female), or to be XX with an SRY translocation (XX but male).

Biology is complicated: pretty much anyone who says it only happens one way or is really simple is wrong.