That post was wrong as far as 17 and up - it's just legal and that's it.
But there is a difference between statutory rape of a consenting minor who really can't "consent" and just rape of someone saying no.
That's probably why the law calls it crazy stuff like "carnal knowledge of a juvenile"
You have to admit although sleeping with a 16 year old girl who is willing is very wrong for an adult, it is not on the same level as forcing her to do something she doesn't want to