There is usually some fatigue intraworkout that lowers the relative intensity and we’ve said 70-80% ish, which includes 5 @ 8. We also regularly prescribe 5 @ 7 or % drops from 3 @ 9, 1 @ 8, etc.
Finally- it’s much easier to accurately hit a 5 @ 8 than 5 @ 6 as it’s closer to a limit set (5 @ 10) and less squishy.
“There is usually some fatigue intraworkout that lowers the relative intensity”
Surly intraworkout fatigue would ‘increase’ the relative intensity, (due to a transient loss in performance and therefore decreased e1Rm throughout the workout) unless you’re talking about dropping the absolute weight on the bar after each set?