If a board RPG admin wants to escape their host's radar, they simply do not post content that'll attract unwanted attention. Or, they post to their heart's content and label their game with PG/2-2-2, which is only a disguise. A board host won't insta-ban you if your game has PG/2-2-3 instead of R/18+/whathaveyou plastered on the front page.
Many board RPGs are rated with 2's, of which many players find it perfect. As I said in another comment, you can get away with a lot of 'graphic content' on board hosts, with PG-13/2-2-2 or 2-1-2. A higher rating isn't necessary. IF staff don't care as much as they used to, about their users; more often than not, a board goes down because a disgruntled player wanted to 'get back' at the game staff, not because the board host staff were policing their boards.
Rules are getting longer and longer these days, with lengthy explanations of: don't swear but you can smoke; don't drink but you can do drugs; don't fuck but you can kiss; don't kill someone but you can strike them, etc. Instead of filling up the Rules with laundry lists, one merely substitutes it all with three numbers.