I haven't spent much time looking at profiles on OF, but I will say that there are a ton of girls that "look underage" on AVN. If they want to use fake ids to get a pay account, there isn't much the platform can do to prevent it. What is not clear to me is that the bank details (where you have your payouts sent) have to match the id you provided so I am not sure how they are getting around that. If you use grandma's passport, the money has to be sent to grandma.

I don't remember what I had to do to get the AVN account open. On Eros.com I have to submit not only my photo id but also a photo of myself that says "Eros (fill in the date)". I have had to do this more than once. I am pretty sure that is what was required on AVN too. That's not foolproof, but it's better than just asking for a copy of id.