What a bizarre mindset. Something's established when it's introduced. For the first time. To the audience. The fact that you can retcon things later to change the timeline doesn't alter when something is established. A New Hope established the idea of Star Wars. Charles Soule didn't establish Star Wars because his book is the first in the current continuity. It was George Lucas.

Hell by your logic if a retcon can change when something's established then retconning invalidates both the Force Unleashed and the Timothy Zahn books, the old ones I mean, because they've both been retconned not to have happened. Therefore neither established anything. It's just a silly line of reasoning.

All of which again is beside the point.