There was no such thing. Let me quote what I replied to: "No, we treat children in a certain way because they are children." That isn't an answer; it's just circular reasoning.
He started very immature, and gained maturity as he aged.
"maturity" is completely subjective to begin with, but it usually boils down to doing things that other people (or society in general) agree with, in a way that they agree with.
Since age is arbitrary, should I have treated him the same at 3 years old and 13, when he was much more responsible and self-controlled?
I don't know. What did he act like at 3 years old? You have your answer, then.