The page you linked clearly explains that they use other search engine sources, which makes your post either wrong or intentionally misleading:
Our search results also include anonymized API calls to all major search result providers worldwide, specialized search engines like Marginalia, and sources of vertical information such as Wolfram Alpha, Apple, Wikipedia, Open Meteo, Yelp, TripAdvisor, and other APIs. Typically, every search query on Kagi will call a dozen or so different sources simultaneously