I'm here wondering why it would make a difference whether the girl is under 18 or not. You could argue that the criminal has to cover up his crime by getting rid of the evidence (murder) because the girl wasn't 18 yet and therefore it makes sense to stop under 18 year old girls from using the platform because they are living evidence, but it actually sounds more like a problem caused by the law itself.

After all, dating apps are an even more extreme version of this. If you're attractive enough, you get to have many one night stands and many murder opportunities.