I think it was just experimenting. I never get a pump from 5-8 rep range. It is great for adding weight to the bar and strength increases, but I felt like something was missing. This way I get to do both.
I am trying out insulin right now, and the pump is even more magnified, so something just felt right about trying it this way, still getting the heavy weight and then pumping up the muscle with higher reps, forcing blood into the muscle, aided by gear and insulin to transport nutrients into the muscle.