In my workouts I always target around 95% intensity, no matter what to ensure the progress.
However I fully understand that my body status, the actual level of my 100% can be changing day by day.
It depends on many things, like:
-diet (how much and what you ate and when)
-sleep (how much and the quality)
-nervous system (stressed, focused, relaxed)
-climate (temperature, humidity)
-and many other craps, like moon phase etc...
Therefore it is important to listen to your body and when you feel pumped and energised go for a couple of extra reps and when you are down a bit easy the load.
It can be a double edged sword for beginners who could always find a good excuse why not to execute the plan, this way - it is a thin edge, you need to learn your body signals.
Bulgarians do this way: if the "plan" says 90% x X reps then they test they ACTUAL max on the very day and they aim the 90% of that on that day. Obviously the max is changing slightly day by day, so does their 90%.
It is similar to what Oni does, I believe, he tests his 100% and he determines the 95% as a threshold - on that day.