> No one ever says how big [DuckDuckBot] is
One complicating matter is that it specializes in DDG's "Instant Answers"; apparently¹ the "source from other search engines" approach really only applies to the traditional results list, while DuckDuckBot is focused specifically on the Instant Answers, effectively optimizing for the absolute most relevant first result possible. So in its current state DuckDuckBot ain't exactly comparable in purpose.
Still, I don't see much that'd be stopping DDG from ramping this up and having it generate the traditional list of results, too. Yeah, obviously the results for quite a few queries will be far from ideal, but if the query already hits one of DDG's curated data sources, I suspect the results might already be better if anything.
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¹: https://help.duckduckgo.com/duckduckgo-help-pages/results/so...