These systems vary by country and you’ll find fault with most of them. They are more often than not rating systems that were introduced to appease a loud group in society, possibly the pious folks were one of those. Society’s natural inclination “to think of the children!” makes these rating systems more about age appropriateness than about clearly labelled content. I can see the logic in your approach to the subject. Logic probably wasn’t the driving force behind introducing labels such as “parental guidance” or “restricted.”

I think it might be easier as a committee to be compelled to come up with an age of people, for whom the content is appropriate, and not argue over labels until they’re blue in the face. Is vaping drug use? How much blood (if any) is required to be labelled violent? Etc. Can this committee agree with a majority vote that 12 year olds probably shouldn’t see this? That’s probably easier.