MYZ Not expert on macs but certainly internal display connection is more complex than screen being connected to gpu frame-buffer like most laptops. DCP is name of coprocessor that manages display outside of gpu and it is entirely possible that it could perform dithering regardless of what gpu does.
Some say strain with Asahi is better so perhaps that could be useful of research - however given how difficult research of display outputs on 'classic' laptops is certainly not something I would wait on.