The old EU, as proven by Lucas, had no bearing to the stories that happened on film.
That's not really true. Where do you think Coruscant came from? The prequels are littered with EU references, proving the exact opposite. Lucas loved his fans, even if he didn't entirely understand their enthusiasm. And for an even deeper insult, Lucas's own non-film projects got labeled "EU" and tossed out with everything else and Lucas himself was dismissed. Sorry, old man, we own your baby now.
My choice of wording wasn't the best. Let me put it another way, Lucas (and Disney) are/were not beholden to use ANYTHING from the legends fiction. While Lucas did put in cameos, when push came to shove, he used what HE wanted, even if it disregarded any legends fiction. The clone wars as described/implied by Zahn is different from the films/series. For a more recent example from the clone wars, the name of the Sith Homeworld is Morribund, NOT Korriban. The old fiction, in this case the name, was swept aside.