Exactly, mpv logic causes it to pick up Nvidia for HW video even if renderer is on iGPU. There is special flag to choose device which solves the problem and Nvidia is kept down
Look at reference implementation. Maintainers resist removing google dependency for no good apparent reason. An if there is persistence without reason - there is a reason.
Also worth noting that manufacturers advertise photodiode count as a sensor resolution. So if you have 12 Mp sensor then your green resolution is 6 Mp and blue and red are 3 Mp