Ratings systems do not work. The MPAA is notorious for a subjective application of ratings that favor the major studios. Independent producers and directors are routinely held to a higher standard. Ask John Waters about how his films are rated by the MPAA.

LL is notorious for subjective enforcement of their policies. They have never had the staffing to effectively police their grid. This content rating system is pretty much just lip service. I cannot see them even wanting to test out enforcement of this unless there is some really horrendous activity in a mainland mature sim that warrants it. Otherwise, it will be business as usual.