His glasses had flat lenses

Rating: 9/10 (12 December 2019)

Watch Costner's face closely. His fake reading glasses have flat lenses. Real glasses, even real reading glasses, have folded lens. The flat lenses are reflecting all the movie making going on in the background. Watch closely.
This was done on purpose, because this film was not made to solve any mysteries. This film was made because everyone involved loves filmmaking. This is a movie about movies. It's a masterpiece, because every available tool (at the time) was used: different cameras, different film stocks, different lights, different crews and at least two editors in the editing bay.
The film references three realities for us: The day of the event, the manipulation of the day after by the media/government, and the lies we tell ourselves.