It's not important if they knew it was wrong.

Actually it is; you're the one claiming that because the brain hasn't fully formed at 15, they can't be held so culpable for their decisions. So answer the question: At what age is the brain developed enough to know molesting a 4/6 year old girl is wrong? And if the problem is because of age, why aren't a lot more 15 yeah olds molesting 4/6 year old girls?

Because we're dealing with NOW the question is whether or not they would do it again,

And you can't promise that they won't do it again because you are not a trained psychiatrist who has worked with the person in question. Even psychiatrists get it wrong, like with Ed Kemper, who only killed his parents as a child, got "rehabilitated" and released, then killed several women and raped their corpses after dismembering them.

American punishment styling of handling criminals is dumb.

It must be pretty dumb in other countries too because their sexual assault rates are up and yet their prosecution rates are down.

https://www.economist.com/international/2020/01/02/why-so-few-rapists-are-convicted

You should want people reformed into functional members of society instead of stupidly asking whether or not the action they performed means they deserve to be punished forever for what they did.

I should have to support your claim that 15 year boys are natural inclined to most 4/6 year old girls when the overwhelming majority of 15 year old boys don't do that. You should not make "boys will be boys" excuses dexter it's stupid, sexist, and morally/intellectually wrong.