"The Holocaust" usually refers specifically to the killing of Jews and not the broader genocide, though this varies. It is also worth noting that about 1 million Jews were killed on the eastern front and are correctly counted as part of the 6 million, but overall if anything you are probably lowballing non-Jewish victims.

I think part of the reason for Jews being a focus of the discussion is that they were the face of the vilification and the Nazis went to incredible lengths to capture or kill every Jewish person they possibly could in the territory they controlled, both in relatively stabley-held civil society and recently taken-over military conquests, which is pretty unusual compared to other genocides. Jews were also far and away one of the most brutally killed and persecuted on a per capita basis compared to other groups (though I think Romani were in a similar boat there but Europe just hates them).