That links "more than 400 sources" to https://duck.co/ia which in turn links to https://docs.duckduckhack.com/#improve-a-live-instant-answer saying "DuckDuckHack is in Maintenance Mode". But https://docs.duckduckhack.com/welcome/how-ias-work.html suggests that these sources are for things displayed at the top, which I see super rarely.
Yahoo gets their search results from bing, so that's the same thing. So this supports my claim.