Aren't most intersex individuals infertile to begin with?

Lots are, lots aren't, I have no idea where to get reliable stats.

the sterilization of trans people is generally at their request

Much of the time, but "you must be permanently sterile to change your legal sex" is a completely unnecessary law. I've known someone who isn't getting a vaginoplasty just in case uterus grafts become possible in her lifetime and the op would compromise that. Trans men don't usually get bottom surgery, so sterility is impermanent (just get off T when you want kids); many do get hysterectomies, but only get their ovaries removed because of legal requirement. And there's no reason not to freeze gametes.

he deeply wishes he had had the 'unnecessary surgery' when he was young instead of after years and years of infections

Well yeah, that's one reason we shouldn't give kids surgeries just to make their junk look normal - so that we can actually believe doctors when they say it would improve their health.