I worked with an SGI 2400T workstation and it came with a 4:3 aspect high resolution monitor (4K I think, different from today's 4K). Later workstations probably had wider screens. However even that old machine could display to a wide variety of screen sizes. I connected ours to an NTSC projector and they were often used for rendering movie computer graphics (though rendering doesn't depend on the display size). If I remember correctly the pixels were square by default, but there was a lot of control over rendering and display. NTSC at that time wasn't even a very firm standard, lots of companies implemented it differently and hi-res displays tended to be custom with no standards at all (used for air traffic control for example).

They used non-square pixels and none of the demos have been stretched appropriately.

I remember the SGI workstations in our campus lab having such an absurdly curved surface.

It made other contemporary CRTs feel like flat screens by comparison.