Once someone is on hormone therapy Their levels of testosterone drop to less than half that of a man. Still more than the average woman, but far less than a man.
Testostorone doesn’t account for everything, as I say, some people are bad and some are not.
It’s irrelevant whether testosterone decreases. Even at half the normal amount for men it’s still ten times the normal amount for women.
In any case, aggression isn’t about the amount of free testosterone in the system.
Testosterone aids in the learning of aggression.
Take that testosterone away and you still have the learned behaviour, just as you still have the greater musculature, the greater bone density, the greater lung capacity, etc.
Imperial China had armies of eunuchs. They didn’t sit around swapping knitting patterns.