He could very well be a genetic chimera. No, not the Mother Chimera, I mean a genetic chimera. Sometimes, when a zygote is fertilized in a way that produces non-identical twins, VERY VERY early in development, one zygote "absorbs" the other. This is often seen in conjoined twins or people who grow up with their twin in their body or whatever, but when it happens at a zygote level, the person can have multiple DNA patterns in different parts of their body, and never realize it.
It could very well be that parts of him are a man, and parts of him are a woman, and those "woman parts" just could happen to be in the hormone centers. They wouldn't be able to genetically test that unless they were able to scrape cells off that particular hormone production center.
A large part of testosterone is produced in the genitals, so if he has male genitals, then he would have just enough testosterone to ward off most of the female effects until late in life, when testosterone levels naturally decline.