DuckDuckGo along with other search engines like Ecosia, Yahoo!, Qwant and StartPage use Bing and/or Google as back ends for their search results, and since Google and Bing/Microsoft (and Yandex, which has its own engine) have been filtering out terms that return "child abuse material" (this includes actual CP, questionable photos of children and loli/shota porn) these engines' search results are indirectly crippled by these upstream filters. Google and Bing's loli-related blacklists aren't new, and certainly they aren't good either. They simply cover extremely vague and generic search queries like "loli/shota + hentai/porn/rule34" because that's how most "concerned internet users" and dumb normalfags find loli porn, so anything outside these terms can bring actual loli/shota porn, like searching "rorikon hentai", "lewd lolis" or a character's name and the word porn.
Still, it shows how loli and shota material is a liability for these companies due to the high amount of retards equaling it with raping children and because it's illegal in some countries (causing Google and Bing to censor it everywhere instead of spending time making filters for these countries).