You note not everybody is the same, testosterone doesn't affect every man the same, you say XXY man, I say every man. I can look around the gym and see men of the same age all looking different. I can do the same everywhere I go. There are men everywhere and they're all different.
So; what's so surprsing?
The medical profession determines that if we're XXY and androgen deficient that we all need the same level of testosterone to begin with. The only time that actually changes is if we say something, either we like or dislike the regime. If you were like me and every time I went to the doctor and said I felt fine, regardless if I did or not, then my doctor never got told the truth. I was thinking he'd tell me if I was looking as I should, not that his questions were the mechanism he used to determine if I had the right level of testosterone.
So I'd go cycle training with other people my age and younger, and I'd see their bodies change, but mine didn't. So there's a clue, their bodies changed in response to their physical activity. They weren't all the same though, they just became more obviously mature.
I didn't want to be a body builder. I wanted to race cycles and win. I did the racing part, not the winning part. But then only one person can win. There were plenty of others who never won too, and I'm pretty sure they weren't all XXY's, but they did fill out, get more muscular, look more mature, more manly.
Now when it came to hair growth, I'm pretty sure anybody, male or female, can take very large doses of tetosterone and grow a full beard. The simple fact is to grow hair you don't need to exercise. Just the right amount of testosterone at the right time will do. And if that time is missed, just upping the amount of testosterone will do.
I missed the optimum time for growing facial hair, so had my testosterone level upped massively. And it wasn't me who noticed I didn't have a typical mans amount of hair, it was my ex. She looked at me and said words to the effect of 'Teenage boys have more body hair than you" and she was right.
Now my ex was a bit heavy, and we wanted a family, and for her to get pregnant she needed to lose weight. So we were at the gym together, for different reasons, she wanted to lose weight and I wanted to gain weight. Well she lost weight. I never gained any whilst overdosing testosterone. Building muscle takes more than just taking testosterone, eating more, and doing weight training. There's something else required as well, maybe the right time?