Sorry, I didn't want to get defensive.
I guess you are right about the drivers, it was just funny to me that I had the
same issue on Windows 10 with the AMD drivers provided by Windows Update on
install.
There seems to be a problem with the drivers that does not affect all 144hz
monitors and can (in the case of the Asus MG279Q) be worked around by monitor
firmware.
I don't know how the firmware might change the gpu's dc clock though.

I attached my verbose xrandr output including EDID.