I just saw an Anti go "why do you have a 'Minors DNI' when you're writing NSFW of minors?!?" (the 'minors' being, of course, fictional) as some sort of gotcha and, like... I thought I've seen everything, but humanity does like to surprise, huh?
it's such a weird argument, y'know? Its not only an issue of legality to keep minors out of NSFW spaces, but almost always to keep minors away from adults who may behave in a predatory way.
and the age of a fictional character is arbitrary and usually only matters for plot / genre definitions. BNHA could easily be about a bunch of college kids, or the YA dystopia book of the week could exclusively be 18+ characters and very little would change.