In particular, I suspect the DACs and gamma buffers used to derive the LCD driving voltages may have some non-monotonic effects, which would definitely affect the test --- i.e. if increasing the numerical R, G, or B value actually decreases the corresponding colour intensity, even slightly, of the light emitted.
https://en.wikipedia.org/wiki/Farnsworth-Munsell_100_hue_tes...
In particular, I suspect the DACs and gamma buffers used to derive the LCD driving voltages may have some non-monotonic effects, which would definitely affect the test --- i.e. if increasing the numerical R, G, or B value actually decreases the corresponding colour intensity, even slightly, of the light emitted.