The “R” rating to “X”, is a cliff in the industry.. The only reliable ratings are, “G”, and “X, IMHO.. Knowing they couldn’t bluff a PG 17, which is the safer bet to draw the teen market and adults, thus the most reliable movie market.. They push the envelope on the middle ratings..
PG, loses the Millennials, and older adults, PG 13 is a dud with only families with grown children as the only available target, today’s teens hate this rating in recent years, and you are correct, no one challenges the younger costumers unless it is so obvious that other adults will/might, complain..
No accounting for people's taste, is there? (Unless they were all suckered in there like I was.)
No cinema I've been to in 10 years even has a way to police who enters a particular theater. Your tickets are taken where you enter one of the two wings. Once in you go into whatever theater you choose.