That demo was my introduction to the Amiga. Whenever I met an Amiga fan later in life I would picture that demo in my head.
Adult, programmer me knows all too well that demos are marketing material, aka "lies you can't be sued for", but really faking 3D rendering is pretty low even by marketing standards. I am extremely disappointed.
This kind of screws with the memories of some interactions I've had with old fans over the years.
You could say it's still true, a lot of graphics in AAA console/PC games could be called fake same way. Precomputed physics and such. That subsurface scattering? Fake. Soft shadows? Fake. Fluid dynamics? Fake.
Although, Amiga could have rendered that in real time too. Just two bitplanes and a smallish area.
I'll point out that once they finally, FINALLY made a memory card for the Commodore 64, that plugged into the megabyte-per-second DMA port, there was a similar bouncing ball demo done for the C-64. Purely by loading whole frames into the memory card and blasting them onscreen as needed, like a page flip.