He actually does a surprising amount of work on the series.
Not only does he involve himself in multiple points during script development (when story is proposed, during writing, final script approval), he's also involved with the editing of the show as well.
The guys who run the show mention they can always just pick up the phone and ask George some question about something or other that was never expounded upon in the films (although perhaps mentioned in books) and they'll get an answer, sometimes a surprising one.
One example is a season 2 episode where they go to Mandalore and you find out about the Mandalorians and George's official take...which is basically everything you've ever read in the EU books and comics and the games is WRONG. I won't go into it because it would take too long, but it's nothing like what Traviss or other EU writers who really delved into their history and culture made it out to be.
The Jedi Master
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Back off, man. I'm a scientist.