I know this discussion is dependent upon on many variables such as training age, time of year, level of athlete, etc…
I like variability, too. I just don’t know why people need to cram it all in 5 days.
I like to rotate a few exercises in and out over a 4 week minicycle. Big lifts (squat, bench, rows) stay mostly the same, but accessory exercises vary week to week.
Yes, submaximal work won’t tax the CNS as much but the muscles in my legs are still doing the work which, to me, makes it more than a small deal. This is essentially why Mike Boyle stopped having his guys train legs every day. Sure, they theorized that separating lifts into quad dominant, hip dominanat, etc… would allow them to get away with it but they were wrong.
I personally like hitting each major muscle group (legs, chest, back etc.) twice per week, once hard and once easy/light. For sprinters, I don’t think its necessary to hit upper body twice, especially if doing cleans.