"Web results" are. "Siri Suggested Websites" and "Siri Knowledge" are not — those are fed by Applebot. "Applebot is the web crawler for Apple. Products like Siri and Spotlight Suggestions use Applebot." — Apple's support document about Applebot.
I've wondered why no one has bought wolfram alpha and used it to power knowledge bases. Certainly it seems cheaper for Apple to have down that as a start point than to start from scratch. Maybe it's too technical for most users?
