This may just be FFG stating for a fact something we've all been overlooking.
Bespin Gambit already blurred the lines of the game's "cannon" standing honestly. Lando is clearly in league with the Rebellion (at the very least, he's a sympathizer; at most, a full fledged Rebel operative).
Being a small box expansion, they could not put time period designations on the missions since it is supposed to be a supplement to the Base set. As such, there are clearly some inconsistencies that you could possibly go from the aftermath of Yavin right into a mission where you are teaming up with Lando. Sure, you could rationalize that Lando has been a covert op for the Rebellion before Han and Co head to Bespin but nothing on film really points to that being the case.
This official "change" really only has one effect, IMHO. To date, the game had a more "EU-esqe" feel to it: you were the background characters undergoing missions that fell between the scenes of the movies.
Now it has adjusted to a more "Infinities" feel where players are able to play a more "What If" storyline and re-write some of the minor events as they see fit.
Edited by FSD


