In theory if the DMD mirrors were perfect little squares, and if the lens has perfect focus, and if the mirrors switch infinitely fast and are perfectly aligned with the color wheel in time, then maybe it’d be fair to call them uniform squares of color. In reality, the mirrors look square, but aren’t perfect squares - there’s variance in the flatness, aim, edges & beveling, and also both the lens and mirror switching blurs the pixels. The mirror switching over time is not infinitely fast, so the colors change during their cycle (usually multiple times per color of the wheel!) Not to mention some newer DLPs are using LEDs that are less square than DMD mirrors to begin with.

All this comes down to the projected pixels not being nearly as square as one might think (maybe that’s on purpose), though do note that squares are not the ideal shape of a pixel in the first place, for the same reason box filtering isn’t the best filter. If your pixel has sharp edges, that causes artifacts.

Take a look at the pixel-close-up comparisons in the projection shoot-out: https://www.projectorcentral.com/Projector-Resolution-Shooto...

Notice how all of them are visibly blurrier than the source image, and even that all of them have visible aliasing.

Also just for fun, check out this interesting video showing what DMD mirrors look like under a microscope: https://youtu.be/KpatWNi0__o