because of innocence?
Viewing post in what is a 13 allowed to create?
The concept of "adult" stuff is a misnomer in this context. Because for content it is bascially defined as stuff that is forbidden for kids. So of course, the response will be, that yeah, kids should not do "adult" stuff.
But why should a 13yo dabble with stuff aimed at 6yo. Guess the age of the average reader of Twilight or Harry Potter. If you think about what concepts happen in these books... that ain't dora the explorer.
Sophisticated might be a better word.
Let's have a look at the popular Civilisation series. Part VI has this rating:
ESRB Everyone 10+,Drug Reference, Language, Mild Violence, Suggestive Themes
That game deals with WAR, for crying out loud. You literally send your troops to death in the meat grinder of war. You slaughter barbarians. But yeah, it is ok for 10yo. "Mild violence". Yeah. Snort.
tl;dr Asking about concepts is the wrong question. In the context of video games it is about presentation.