I also may not understand. What I read out of it is that Cortana sends a Bing search request to your default search engine (Firefox or otherwise) and Firefox t

I also may not understand. What I read out of it is that Cortana sends a Bing search request to your default search engine (Firefox or otherwise) and Firefox turns it into a search request to its current default search engine. The existence of a Chrome plugin for doing the same indicates that until this change, Cortana searches would go to Bing no matter what.