^I notice they don't call him a Dark Jedi, though, either. I've noticed that with TCW, too, in regard to the non-Sith darksiders on that show.
Frankly, I don't know why the current regime is so reluctant to use the term; they're always going "Well, such-and-such isn't a Sith, but he does use the dark side of the Force and yada yada yada". For God's sake, just say the non-Sith darksiders are Dark Jedi and save yourself the effort of using so many words to say so very little.