Oh, man. You just asked a mouthful. And I am not sure if I can completely answer it. The Principle of Critical Drop off is something like, “Whenever you do a set in which your training load or reps drop more than 20% beneath your max, you should terminate working that bodypart.” Right? I am sort of going from memory. That’d be a great guideline for a strength cycle. And also for long term bodybuilding.
But for a short term bodybuilding cycle (say, if you wanted to add muscle over four weeks), you would have to find some way to jack up your intensity every workout, regardless of strength gains. So I think that continuously adding reps, shortening rest times and adding pounds is mandatory.
For instance, I have seen people add muscle doing GVT who actually lost strength. And they would have been doing work in excess of the Principle of Critical Drop Off. (ie. If they tried a 10x10 ad their reps were 10, 10, 10, 9, 9, 8, 7, 6, 5, 6, then they were a full 50% behind their max reps on the 9th set, right?) But they still added muscle!
I am not sure if I am answering your question, but it is an interesting thought.