Converting light to bioelectrical signals that the brain can react to takes longer than biological sound signals to be processed. It’s evident already that the timer with auditory start signal is consistently faster because the OODA loop significantly shortened. The audible stimuli cuts out the “observe, orient and decide” and leaves just “listen and act.” The orient happens before the timer ever starts.”

These are fair points. An auditory start signal to start timing an already-known, pre-oriented event is the best case scenario, equally for everyone.

All humans will be slower with other variables at play including those with whatever tactical training is currently fashionable. A known-in-advance drill begun with an auditory start signal after the person has prepared and made ready is the best-case scenario in terms of reaction time and performance, probably unrealistically so.

However, a person that is measurably slower with the easiest possible evaluation will be even slower-er with those other variables in play. A fixed, known-in-advance drill shot on motionless, non-threatening targets is much easier than real life. A failure on such a drill means the person will just get much worse when things become more varied and serious.

Once again, “failure” means missing a reasonable standard by a fair margin, something that wouldn’t happen if fundamentals were squared away.