I feel like what you're talking about gets really close to the Roth test and I can see how that might be a factor for Apple pulling your app but leaving others.

There's a lot of amateur porn stars on social media that call themselves models. There's a lot of models that aren't.

I don't know how you create an app where people pay money to chat to models with racy instagram photos and discriminate between who's making pornography and who's not.