This is an article written by a man who naturally didn’t go through puberty (due to a medical issue):
https://genspect.org/frozen-in-time-when-puberty-doesnt-happen/
“What I’ve learned since is that when the adolescent brain is starved of sex hormones during the critical window, the damage is permanent. Autism is five times more common in people like me, ADHD several times higher, and severe intellectual disability nearly eighteen times more likely. A quarter of us never become sexually active, and three-quarters of us never have children. Executive function, attention, and processing speed are all measurably lower. I live with ADHD and learning disabilities that no amount of therapy will ever fix.”
So, in answer to the questions above, even though his medical problem was eventually identified, and, at 15, he was given exogenous hormones, he never caught up with his peers.
I have seen videos of him speaking (he spoke at some Genspect conferences): he sounds like a very much younger person than he actually is.