I've read Bagget's stuff on AREG as well. Good stuff. He does make it a little more readable. AREG trains you based on your current neural efficiency at training day. You literally only put out exactly what you have, nothing more, nothing less.
The flaw with a standard routine is that it doesn't account for shifting neural efficiencies. If a routine calls for 4 sets of lat pull, what if you hit your first form drop off at 3 sets? Then you are overtraining. What if you only do 4 sets and you could have done 8 sets? You undertrained.
With this system, you determine your max on a given lift in a given rep range, then reduce your weight by 6-10% (depending on when you want to be in supercompensation), and perform as many sets as you can in that rep scheme until you hit your first form drop-off, then that exericse is done. This is also how you can control your volume in such a way that you can train a muscle three times a week and not overload your CNS. It is a beautiful system, and the results you will get are incredible. Not only that, because you are spreading the volume across the week, at no time do you feel just zapped (a big sign that you're overtraining).