Either way, I'd guess that 95% of these underage relationships go completely undetected and unpunished even here in CA.

How big an age difference we talking about?

My 1st girlfriend was 19, and she was quite open about having dated guys in their late 20s and 30s starting when she was 15.

Well, that's not OK. I don't know how to stop it though, if you are correct that it is the girls going after the guys in most cases (rather unlikely IMO).

Nymphette is a reference to the most famous book on this: Lolita. From a wiki on it: "The term means "sexually precocious young girl," and was used by Humbert as a way to justify his predatory actions towards Dolores Haze, his victim. a Lolita or nymphet was thought to be a young woman who purposefully pursues and manipulates older men into sexual situations... By around 2014, on tumblr, young women took on this trope for themselves... Tragic love, new sexual experiences, rebellion, drug use, toxic relationships, intense friendships, and self-destructive behaviors are some common motifs."

Sick dude. They literally called themselves by a term used by a pedo to justify child molestation? What's going on?

That's why "don't stick your dick in crazy" exists, because dating/fucking these girls usually ends up with them having a "honeymoon" phase trying to get their hooks in, followed by them blowing up on you and going psycho, which can sometimes include false accusations.

How would you know though, in the 'honeymoon' phase?

I've met and known a number of these crazy girls. None of them started having sex at 18+.

Obviously. But I don't think they were having sex with 60-year-olds. A little older is fine.