nothing was a perfect square
By the way, there definitely were "perfect rectangle" (I assume you don't actually mean "square", but rather just non-curved) CRTs later on, or at least very nearly so.
But yeah, maybe I should try the project you've linked, it may really be a good simulation of it. (Though I wouldn't want to use it as my "regular" terminal.)
It always blew my mind that you'd buy a new videocard, and plug the big CRT monitor in it, and it would switch between different resolutions. Precisely because the holes and pixels don't line up, they supported a huge range of resolutions and it didn't look as smeared as on LCDs.
I think the mask in the CRT itself also contributed to a kind of subpixel Anti-Aliasing.
And I've never seen this in real life, but it's amazing, using the hardware implementation to force 1024 colors out of CGA?! https://int10h.org/blog/2015/04/cga-in-1024-colors-new-mode-...