Parents guides are not as detailed as they should be

I often check the Parents Guide section for whenever I watch more mature movies due to the fact I get quite uncomfortable watching certain things and so does my gf. My friend recently recommended me a movie called “The Story of Mr. Sorry,” it’s a Korean film school animation which I am aware is very niche. However, checking the parents guide I read something along the lines of “there’s a sex scene between a couple that takes place in a girls mind… the last part is really disturbing, I’ll just leave it there”: isn’t it the authors job to be fully detailed about what contents are in any given movie? I just feel bothered that I and my gf had to witness something really disturbing (since I’m not writing a guide I will ironically not go into detail for now as well). I like would like to know what the criteria is for becoming a Parents Guide author for movies and if so if I could become one because I could do more than half the better job most of these reviews are on letting people know exactly what they’re getting into with these films.