I wonder though, updated pixels might not have the same latency on the whole screen, and it might even be affected by some updates mechanisms, like panel replay. I.e. it would have been interesting to also measure the screen position as a dimension.
Also, both the input latency (usb controller, and its driver), and screen latency (input latency + processing + update delay) are supposedly also affecting all measurements, but hopefully somewhat consistent or at least filtered out.