Funny, I always thought Alien and Aliens were 4k all the way through. I guess they were just 2k finishes of 4k scans.
As for Star Wars, maybe the work took a long time? Especially if they were working frame by frame at 4k resolution. By "Star Wars" maybe he just means the first movie. Maybe that's all that was done by the time the blu-ray happened in 2011 and so they still used the old master for consistency's sake.
Like I said, there's no footage from Jedi in that demo reel. Maybe they worked on ANH several years ago and only recently worked on Empire.
They could be working on RotJ right now for all we know.