Yes, humans have biases. There's not a way around it.
> What does that mean when applied to duckduckgo's tweet from 2019?
Yes, that tweet is obviously a vague marketing message, but if you read the entire quote in context, it was in reference to filter-bubble biases. It wasn't a claim that DDG employees are somehow superhuman creatures immune to human biases. Obviously that's a ridiculous interpretation.
Here's the source, in context:
https://spreadprivacy.com/why-use-duckduckgo-instead-of-goog...
Search results are created by humans and intended to be consumed by humans, so yes. (And just to head it off, a web crawler is ultimately just an abstraction for the humans who will later consume the search results, it just happens to have particularly fast and strict browsing habits)
Now that said, accepting that "(un)biased" is an extremely broad term, I'd very easily believe that the intent of the tweet was to point at some specific type of bias that DDG (at the time) intended to avoid.
Short answer yes, if humans are involved in making something it’s going to be subjected to the biases of those humans.
https://nyupress.org/9781479837243/algorithms-of-oppression/
Frankly, I'd be surprised if there weren't implicit biases already there.
But this is something new. Its overt, explicit.
All search engines are explicitly biased. That is the point, they generate a ranking of results. Heck even how you tokenize text is an explicit bias of what you match against.