Some I believe, some not. There are so many revisions of the script from the first draft to the final cut of the film you could call a lot of stuff "unscripted." I did a quick search for the Empire Strikes Back script and there were three completely different versions. The first draft bears very little resemblance to the final movie, and implies a sex scene between Luke and Leia. Then there's what I guess I'd call a "middle draft" that was pretty similar but still had major differences, such as Vader not telling Luke he was his father, and "I love you!", "I know" replaced with a more long winded "I love you, I couldn't tell you before, but it's true", "Just remember that, 'cause I'll be back!" I'm thinking that was the script they started filming with, meaning they did change the exchange to shorten it and make it less hacky.
I believe this one because of the similarly hacky and long winded exchange from "Attack of the Clones", that went mostly unchanged because nobody was questioning George much by that point.