The idea is that the angle of view of the camera is duplicated when a print is viewed at a distance of approximately its diagonal. This is 53deg regardless of the shape of the print. For 35mm full frame it is actually about 44mm rather than the more common 50mm. Again, all this is based on assumptions about viewing distance, etc.,which may not be valid in all cases. You can also get the effect by looking at a small print with a magnifying glass.
Panoramic formats fill the visual field less than just a very large nearly square one.
This is one reason for the choice of a nearly square format for Eye Max rather than a wide, narrow format like CinemaScope or Panavision. If you have been to an Eyemax theater you know the very large image is nearly three dimensional. A good eye can distinguish a mesh of 1mm period at a distance of 3 metres. In this regime the eye is in fact a diffraction-limited lens. Unfortunalely this holds only for a few degrees of field.