Well, not completely skipping it but performing the warm up set(s) after the 5 mastery sets. For example, I will try for mastery of FL/PE3 next week and I would like to do it before my 60 reps of bHBR. I would then perform the rocks as a "cool down" after I hopefully pass the 5 sets.
What if I fail then on the cool down, would that mean no mastery after all?