Re: "the monolith is a representation of a wideframe cinema screen rotated 90°."
There is no fixed ratio for Cinema widescreen. There are differing film frames, anamorphic lenses. But the print is "matted" and the projectors have adjustable matte. The 1:1.66 was once popular.
Flat or Matte only ratios common: 1.66:1, 1.75:1, 1.85:1, and 2:1.
There have also been various actual frame ratios by varying the number of sprockets per frame.
Anamorphic uses barrel distortion so filmed and projection ratio doesn't match film frame size. The negative can have a 1:2.35 to 1:2.55 compressed image. Ben Hur was 1:2.7, I think.
Some pre WWII WS used three linked cameras and projectors.
Only TV sets with no projection are fixed ratio.