The page you link to talks about the search results that come at the top of the page, eg a Wikipedia or Trip Advisor result. The actual search itself comes from Bing, and it’s more than likely that the top page banner also is processed via Bing.
Edit: However, the Wikipedia page does provide more detail, which proves you right and my assumption wrong:
DuckDuckGo’s results are a compilation of “over 400” sources according to itself, including Bing, Yahoo! Search BOSS, Wolfram Alpha, Yandex, and its own web crawler (the DuckDuckBot); but none from Google. It also uses data from crowdsourced sites such as Wikipedia, to populate knowledge panel boxes to the right of the search results.