I'm pretty sure reaction time doesn't matter, as long as both players have the same reaction time, right? Like, reaction time could be 10 minutes and if one player sees the stimuli 1ms faster than the other, then they will react first and (assuming their decision making is correct) "win" the interaction.

The next test of usefulness would be real world variance of reaction time between people. For high level players, I would expect it to be very similar, and thus potentially a few ms improvement could take you from slower to faster than an opponent. But "very similar" is doing a lot of heavy lifting here since I don't have exact numbers to look at.