Brain development is the process of reaching mental capacity. Until someone reaches an age where their brain has developed enough they don’t have the mental capacity to make certain decisions like consenting to sex. Some people’s brain development doesn’t work right and they don’t reach that mental capacity or they have an injury that causes them to lose that capacity, but at no point is a 13 year old’s brain developed enough to have the mental capacity to consent to sex.

I was just summarizing the obvious thing that has been pointed out multiple times. I doubt it will sink in this time either.