Zahn used the term Dark Jedi to refer to Palpatine and Vader. I guess he had no idea what a Sith was?
I mean other than wanting The Noghri to be the Sith race, and Vader Lord of the Sith.
I mean i’m glad the Old EU Aka Legends has been left alone they haven’t gone back and given darth names to all the non Darth Sith Lords, or retroactively gave them all red lightsabers. And they didn’t edit the timeline or backstory Zahn had in his trilogy about the old Empire, the Clone Wars, they didn’t correct the ideas of the Jedi pre prequel to homogenize them with Lucas.
What i hate is the need to believe it was all one big consistent canon when it never was. KJA was full of it when he wanted to write that tome about the history of the Star Wars universe, never mind the published Chronology was way different than promised. He promised the existing EU fit the prequel. I mean i know there are fans of these things, but i understand why Disney binned it all. It didn’t fit Filoni Clone Wars either. So they said we’ll put it in the trash bin and call it Legends.