Ah, the classic "misrated submission" case - it happens every once in a while, no matter the type of content, and no matter the Portal...
It's up to us to take action on these to get their age ratings corrected, so for anybody that might be interested in keeping the grounds properly suitable for everyone (and also in getting whistle points, on that matter): keep an eye on submissions ratings, watch out if they're marked as they should, and flag them if they're not, so moderators can be aware and make the change.
TinFoi
Now I sit back and relax, then wait for the hate comments to come in!