The history of search engines is more complicated than most people realize. There's nothing weird about a search site using a different engine than you expect. Someday it could use different ones, or someday it may deploy its own.
I think other than Google that pretty much every site has had engines change over the years. IIRC Microsoft had a search site before Bing, for instance, and IIRC AltaVista changed search engine quite often as it struggled to retain relevance. In general, it's not really the engines that people are upset about, it's the parasitic stuff attached to it at the gate entrance.
Also I'm pretty sure it doesn't use Google. Last I knew Bing is used.
