The phrase
"system fatigue" refers to feeling tired or overwhelmed by using or dealing with a certain system or process for a long time. It can happen when we become exhausted or bored with the routine or complexity of a system, leading to decreased motivation and effectiveness.
Full definition
My reasoning is that I would more likely reach failure during each drop due to metabolic factors or
nerve system fatigue and not muscle fiber fatigue.
By training heavy enough to ensure high muscular tension, the nervous and
neuromuscular systems fatigue long before we are able to push the boundaries of metabolic stress.
Meditation, or even just deep breathing, is an excellent way to reduce your stress levels, thus reducing the chances of muscular and nervous
system fatigue.
However taking in consideration your point about drop sets / clustering possibly fatiguing the nervous system more so than the muscle fibers, doesn't this argue in favor of an approach of periodisation from high reps / light weight to low reps / heavy weight over several weeks as then you are focusing on the muscle fiber types and lessening the impact of the nervous
system fatigue?
This can be time consuming, as training at higher intensities (lower repetitions) also requires more rest time between sets due to central nervous
system fatigue.
The reason why we work in the 60 - 80 % range so much is because working in this rep range allows us to prescribe higher volume to our athletes without accumulating a ton of central nervous
system fatigue.