If I had to guess on the percentage of total reps done in the range you are describing we might be close to 15% but my guess it’s below that particularly since you are talking about >85% of a 1rm, I believe. I do agree that some work, at some point, needs to be very near or at maximal levels for that set-rep range however I pick my battles and am sure to only do this when I’ve accounted for that with a drop (ala vertical integration) in intensity and volume of the sprints and mb throws/jumps
If I were to do so more frequently it would come at a cost to the other training elements from my experience. I will, by week 11 of the fall have the athletes work up to 95-100% of their 3 x 3 best and many can go beyond this and we let them do it. However, the weeks leading up to this are sub-maximal efforts with increasing int. over those weeks. There are peaks in intensities for sets/reps in weeks 3, 7and 11-classic three week intensification schemes with unload weeks in 4 and 8. Week 7 goes up to about 90-95% of the best for 3 x 5.
My belief in the submaximal loading principles comes from discussions with Stone, viewing their programs and workouts but over time and most importantly through my athlete’s training and my own.
Regarding the leaving of multiple reps left, for sure I subscribe to this but more reps should be left earlier in the block and fewer as the weeks go by within the block. Typically the intro. micro, for example, done around 80% of the set-rep best has about 4-5 (for 3 x 5) reps left in set one and 4 reps left in set 3 in the way I’ve done it previously. So during the block as percentages rise, as expected, the number of reps left drops.