DDG does operate their own crawler[1], though they also do still rely on third parties[2].
[1] https://help.duckduckgo.com/duckduckgo-help-pages/results/du...
[2] https://help.duckduckgo.com/duckduckgo-help-pages/results/so...
[1] https://help.duckduckgo.com/duckduckgo-help-pages/results/du...
[2] https://help.duckduckgo.com/duckduckgo-help-pages/results/so...
This refers to the actual search results and if they used their bot for that I don't see why they would say "multiple partners" instead of "multiple partners and our own crawler". The fact that they don't have their own index is such a common "complaint", and this page is often referred, so if they really used their own bot they should have added that a long time ago.
And it's not just a legacy page they have forgot to update. It keeps being updated. In 2019 it said:
"We also of course have more traditional links in the search results, which we also source from a variety of partners, including Oath (formerly Yahoo) and Bing."
It's interesting to note that back in 2014 the page looked like this: https://web.archive.org/web/20131202065705/https://duck.co/h...
Here they talk about their own indexes getting bigger but at the same time admitting that "it seems silly to compete on crawling and, besides, we do not have the money to do so". Completely understandable but also interesting that the current page doesn't mention their own index at all. Maybe they used to have a goal to build their own independent index that has now been dropped?
All in all, I think it's safe to presume that their own crawler is only used for Instant Answers etc since that's the part of the sources where it's mentioned. Or at the very least used to such a small extent in the actual search results that it would be disingenuous to even mention it as a source.