There may be some validity to this but I'm not sure I completely agree. Competition or really airshow aerobatics where margins with the ground are much lower, require reaction times where I suspect a less than a second late can mean an accident.
Scuba diving in my experience was a slow sport. Based on the assumption that he had the background and high experience level, I would think that he would have had the experience for this kind of dive. In fact, I suspect that the actual frequency of the extreme depth dives is fairly infrequent for guys like this and are interspersed with a lot of shallower dives although that is just a guess.
When we look at the causes of this accident, the lessons learned are not that there was any reaction time problem but decision-making such as having the flashlight located the way it was which got tangled in the line and the decision to expend a lot of physical effort in the recovery which appears to be a direct cause instead of cancelling the mission and trying again another time with a new plan when things changed. Perhaps in such extreme dives, if things don't go near exactly to plan, it is time to abort the mission.
My knowledge of this technical diving stuff is not a lot. I'm not sure if more frequent dives would make one more used to the narcosis effects of that depth or any depth.