The people who are in favor of allowing public 18+ activities can scream out anything you want as a reason for continuing to break the game's rules but it literally is irrelevant since you're still breaking the game's rules and if you get caught will be sent to gaol over it.
As far as I'm aware from my time on the forums and reading the posts from people who have been caught, they were all public cases. The OPs in those threads were blatantly advertising ERP services either in their post or in their carrd (like I said before, we can assume GMs are taking these as evidence now if posted by the people involved in the actual venue). Private ERP (as in, two or more (if you're spicy like that) consenting adults in their own room going to town) has not been targeted and personally I don't think they care (like Saefinn said in their previous post).
The massive issue is coming in when people are taking it public and advertising selling sex as a service and trying to make money off of it. That is a literal brothel setting and it's something that Yoshi has already stated PUBLICALLY that he is against and encourages people TO REPORT IT. (Source: https://forum.square-enix.com/ffxiv/threads/392166)
To the OP of this thread: Instead of coming at the people who are reporting it (Some are malicious I will give you that and I don't encourage it at all if it's not for the right reasons), recognize that selling sex in a 13+ game is the problem and people who do have an issue with ERP in this game will report you about it. Going underground and hiding the truth behind a false PF ad or whatever else is used to advertise will still get you in trouble if someone decides to screencap your interactions. In fact it might even turn out worse since you're intentionally trying to hide it. An RP tab won't change the game's or Yoshi's stance on brothels.