This is the end result of the "cartoon=for kids" mindset, people.

So, as a more serious response…

I think that the original article was written at some point around episode 6 in the anime. Her focus on the relatively mild sexual themes in the TV series is explained pretty well by that. She had apparently heard that the show was oriented toward adults, and so far in the show that looked like the most obvious reason. Had it just been a few off-color jokes and distant/censored nudity, she might have had a point.

The problem is, the author adamantly refused to acknowledge that the manga even existed, despite the fact that the anime had followed it almost religiously up to that point. That's fine if you're writing an opinion article based on your response to a series, but if you're recommending it for children, not so much. There are definitely 12 and 13 year-olds who could watch this show and enjoy it. The same is true for similarly violent action or horror films, though. I couldn't in good conscience recommend Friday the 13th for a 12 year-old, even though I enjoyed it at that age.

Just…if you're going to recommend a series for children, make sure that you do your research. If you don't want to spoil the show for yourself, but people are talking about how horrific it is and posting memes that make it pretty damned clear that something abominable happens to two children in an elevator, maybe just hold off on the recommendation until it's done.