Adding to what a couple of others have said, I believe this is pixel inversion, not temporal dithering. One clue is that it happens on all colors except for pure white. For many screens that I've tested (but not all screens), pixel inversion is worst at fairly light colors (such as #A0A0A0) but is difficult to detect at pure white.
In fact, I think it would be very difficult to design a test like this that measures temporal dithering because you somehow have to control for pixel inversion. Perhaps the best you could do would be to test a series of consecutive colors, like #A0A0A0 through #AFAFAF and try to determine whether certain colors in that range flicker more than other colors in that range. Assuming a 6-bit panel, if roughly 3/4 of those colors flicker more than the other colors, then the additional flickering would likely be due to temporal dithering.