"Marketing messages can claim almost anything, but a privacy policy has legal status." - Robert E.G. Beens, Startpage CEO and Co-founder
If you have questions, let me know.
If I can't ssh into their servers and have a look-see or run my own instance, then their claims are unverifiable.
And, it happens that System1 is interested in "capturing" that revenue from contextual advertising.
"System1 is interested in Startpage's ad revenue, not its data," the company said. "The reason a company like System1 openly owns other search engines and consumer tech products like Info.com and Mapquest is that they want to capture that ad revenue that is slowly shifting to private search engines. There has been a steady increase in people using private search engines and therefore a steady increase in their revenue. It is a growing market that they feel will continue to thrive and grow." (https://www.computing.co.uk/news/4017337/privacy-focused-sea...)
That being said: At the end of the day, it all comes back to trust. Even with OSS, you have to trust that they won't change the code. And, you should use products that you trust to best protect your privacy.
Advertising on a search engine is main form of revenue > pays employees > updates > keeps current users and gets new users. You could make the argument for crowd sourcing, but it doesn't always work.
FYI, Ads company brought up Startpage. Despite their public statement with privacy for Startpage, I don't trust them since they can 180 it without any repercussion.