I wasn't aware things were so different overseas! I've been seeing R movies in theaters since well before I was 18. And in quite a few of those cases, I absolutely should not have been allowed to hahaha.
I'll never forget when my dad took me and a few friends to see Harold and Kumar 2 when we were about 12, thinking it'd just be some funny boy comedy, and calling everyone's parents after the movie ended to apologize.
Definitely seems like you've got the superior system over there. I was baffled to see that 5 year old in the theater.