Yeah, it’s a “sourced from a release print” thing. They got super lucky with the 4K83 print since it was (assuming I remember right) a show print that’s a couple generations closer to the negative than a release print would be, so it was A) rarely projected and thus in much better shape, and B) not nearly as contrasty, so you don’t have the crushed blacks or clipped whites that the 4K77 print has in some areas.
Yeah, the 4K83 print is simply stunning. I’ve only seen one print in better shape, and that’s (what I’ve seen of) Poita’s Empire print. Which is pretty good news on the Star Wars preservation front…