Ditto for asking Siri anything that she cannot handle via specialized search conduits (weather, sports scores, etc.). Anything else ends up as a web search powered by Bing, and its tallied even if it was useless and unused.

This often happens to me when I'm exploring the edges of what Siri can do (which is much less than Alexa or Google's assistant). It also happens when Siri mis-hears me and can't properly route the search query to weather, sports, or whatever handler would have been appropriate.

And note that while it is possible to change Safari's default search engine, it is not possible to make these Siri searches run on anything other than Bing. I'm sure Apple is being paid handsomely (and keeping some valuable data out of Google's hands).