Blooey This confirms my theory that specifically on XDR mini-LED Macs (such as your 16" Pro) there is some additional dithering.
I most likely suspect is coming directly from an "8bit + FRC" panel in the Pro that is receiving the Mac's 10bit signal, similar to external monitors that include their own FRC.
What seems to be the trend is Stillcolor makes some degree of improvement but doesn't truly "fix" XDR M1 Macs… but on LCD M1 Macs like the M2 Air, Stillcolor has much better results and can significantly improve the display.
Remember that all XDR M1 Macs use what is called "hardware reference modes" for colors and try to hide away the standard color profile menu. On the other hand, LCD M1 Macs use standard color profiles just like Intel Macs. There is definitely a significant difference in the color management pipeline between display types.
It's actually still possible to force an XDR Mac to load a color profile, but the interesting thing is whatever white point it has will actually be multiplied by the white point of the reference mode. This means that "reference modes" are an entirely different layer of color processing (probably done by the DCP firmware instead of the OS) and not just a simplified "abstraction of color profiles".
(Interestingly enough, the Studio Display is the one counterexample — it's a standard LCD, but uses the new "hardware reference modes", unlike the other Mac LCDs. I would avoid the Studio Display.)
The M2 Air also claims to have 1 billion colors (10bit), but potentially, the 10bit to 8bit + FRC down-conversion is done via the GPU on the Air instead of on the panel itself. (I've seen a few Windows laptops do 6bit + FRC entirely on the GPU, so it's certainly possible.)
This may be why M2 Air users are reporting both better improvements in screen comfort and also more obvious changes in banding.
I really wish I had an M2 Air instead of my XDR M1 Pro so I could see the difference myself 🙂