Yes, I know about notebookcheck for many years. It would be easier but I had access to these devices before discovering this site only recently and recognizing symptoms.
I have tried HDMI, displayport, usb-c, and from nvidia 4080 and hdmi from ryzen 5700g iGPU to the Eizo and I can still measure dithering even when output is set 8 bit mode to avoid potential 8 bit + FRC feature. I also tested a quadro k4200 running on windows 10 potato edition via displayport and still see dithering. I no longer have the Eizo but I still think it is more likely my gpu/ software combination doing the dithering.
For the legion laptop, I have the igpu disabled in bios for testing all external monitors. In NVIDIA control panel, I have tried both 8 bit and 10 bit output. I have tested two T480s both running on intel 620 igpu, same screen specs, same os build versions and drivers, but different panels and differing dithering results. I do this in case it is helpful for others and I do hope more review sites provide more testing beyond just backlight flicker.
Based on posts on this forum, it looks like dithering depends on a combination of software (OS, drivers), video card model and the firmware/bios, display, and perhaps even sample variation from manufacturing defect but I not sure about that. For the uperfect, I tested using usb-c at 144hz. If I understand correctly, others are saying dithering is "baked in" to these newer nvidia and amd GPUs now.
No idea what AAS matrix is. Still looking…*