A: Our reasoning for not doing two X sets is that X Reps take so much out of the muscle that doing a second X set of the same exercise is almost pointless (you can tell the muscle has been taxed beyond its capacity by how much you have to reduce the weight for the next set after your X-Rep set).
That’s why we went back to using the strategy that worked so well for us during our transformation X-periment: a straight work set prior to the X-Rep set. That works so well because the straight set acts as an extended warmup. It insures that your nervous system is primed and the muscle is ready to fire with maximum force. Most bodybuilders rarely warm up enough, and they usually don’t go heavy enough to prepare the nervous system for their first work set. That’s why on many exercises it takes a few sets to “get into the groove.” We want to be in that groove for our X Reps set, and the heavy straight work set that precedes it gets the job done without overtaxing the target muscle.
Your suggestion of a straight set with X Reps at the end followed by a set with only X Reps would be worth experimenting with. Just be sure the target muscle is warmed up thoroughly before that first set that includes X Reps.