The talking heads interviews were shot on 35mm film. A 4K scan of those original elements is beneficial. The film clips themselves are whatever duplicate quality was available in 1995, so they are what they are. In other threads there have been comments that Rebel Without a Cause doesn’t merit...
I know some people are like that with documentaries. Once they've seen them, they've learned the information and never need to watch them again. For me this is one I will never tire of watching. Every 5 years or so I will pull it out and watch it again, like an old friend. So the 4K bump was...