That is a kind of shitty response from World and seems a little condescending to me, but tone is difficult. You are welcome here and I would rather you stay and interact with the rest of us than leave the fediverse. Your voice matters and I didn't have the same outlets when I was your age.
If he knows how to use [fediverse sites][, he is] prolly already using Linux too... Anyone with Linux skills will figure a way around anything online [to be honest.]
Yes, the same as if I lock a door someone breaking the rules will just climb in a window, and that should somehow be okay but isn't.
I think it's less about protecting the kid but about liability. You can just enter under 18, but they have to do something when you boast about it. It's not as if check your ID.