Oh, I agree - I based it on what Brunnis himself was doing comparing the press vs LED tests: differences were minuscule. See it here: https://forums.libretro.com/t/an-input-lag-investigation/4407/524
But he did have a 240fps cam. I'm not sure if I can be bothered myself, it's just an idea. Overall it's all just out of curiosity and old benchmarking habits, which I have since the days of 3dfx cards :P I don't need this to prove anything to myself or others, since I can live with this lag as it is at the moment.
One test though I would definitely would like to conduct is to take some people who claim that are "sensitive" to lag and do some blind trials on multiple setups with various slight differences. I think the results could surprise a few, especially those who swear that 1 -2 frames of lag makes games unplayable for them :)