Nervous system stress/spinal load also plays a big part in maximising the amount of stress you an out a muscle group under. Louie Simmons famously has all his lifters do a fuck ton of belt squats because you can do way more of them than regular back squats because there’s no stress on the lower back and less stress on the nervous system as a result. I guess this is pretty similar to what you’re saying with the fatigue-signal stuff though.