This help page explains the situation best:
Our intention is to not auto-correct searches. That is, we intend to
completely respect the query you type in, and (in some cases) display
a 'Did you mean?' link at the top when relevant.
However, there are a few outstanding major bugs in this area that we
are working to resolve. As a result, you may see some auto-correct
behavior in the search results.
Unfortunately, these bugs involve a bunch of APIs that are mostly out
of our control. We are both working around these bugs and also working
to get them fixed .
For some queries, it has been a little slow to resolve, but rest
assured that this is a top priority. In any case, specific examples
always help as we may be able to easily add more workarounds.
(Thanks for the specific example!)
I'm David from the DuckDuckGo team - if you want proof, e-mail me at david (at sign) duckduckgo.com.