That's not entirely true though...
The CW storylines aren't (at least not all of them, or even most) written by GL, even the movie. GL has input, but he has had input into other EU as well... He's had input on novels. He had input on Zahn's Trilogy when it was being written because he didn't want certain things set up as they were due to starting his filming. The majority is left to others to do though, and Dave Filloni's the guy doing most of the decision making on Clone Wars 3D, and he's trusted to do so. That's why he has the whole "Plo Kool" stamp and stuff.
We've been over the whole "EU" topic again and again, but Lucasfilm's OWN stance is that the films are the only "canon" for lack of a better term... This includes the novelization of Star Wars, partially written by George Lucas, but the films trumped that obviously and it has inconsistancies. The only changes they've really made are that they don't like calling it continuity now I guess, and rather just call it another level of canon. It's basically the same though. Till they decide to change that stance though, then CW isn't being written and run entirely by Lucas himself, and it's not considered part of the 6 film saga, so it's still EU by LFL's definition.
I don't recall having seen anything saying Lucas was writing the stories for Clone Wars 3D though. That makes me wanna check the DVD more closely now, haha... He's got input for sure, perhaps a lot more interest in it as well, and the things he personally approves could be considered as canon as the films, but who knows what all he approves and what he does not? Hell, the original CW3D storyline was turned into a movie because Lucas saw it after it was either written or maybe roughly finished, and thought it'd make a good feature film launch rather than just television (you can even tell where episode breaks were if you're paying attention when watching the film). There was even an interview with Lucas somewhere, where he said the stories of the Clone Wars didn't particularly interest him as much as they did everyone else, and that he really felt their story could be told better through other media (this was before the CW3D toon was announced though, probably during AOTC?) then because to him the Clone Wars were just a plot device about the story he wanted to tell (skywalkers), and so he was leaving it up to the other portions of his company to hash it out.
I'm not saying anything BAD about Clone Wars, by the way, I'm just saying what Lucasfilm has put out there as their standards of canon and official continuity... They're clear, it's not foggy or anything, and the CW3D series doesn't fall under their standards of canon... When people are really into something I think they're quick to accept it as superior to other EU stuff to a degree, but ultimately it's all the same stuff in different forms of media... Lucas's word is the gospel above all, but ultimately Clone Wars3D is "approved" just like Splinter of the Mind's Eye or a wealth of other materials. I'm not mad at them when they dump on EU that's already established, I just think the writers could conjure up a little more correllation with the EU. It'd be neat to me to see CW-era EU characters (other than Assajj) show up even, but it doesn't appear to be a priority or anything. I'd like seeing some ARC Troopers though or something.