I have a theory about this: fatigue. I recall the first time I took the test. I didn't sleep great the night before, got maybe 5 hours or so. I thought a little extra caffeine and sugar would help get me through the exam, so I drank coke (pretty normal for me) and at chocolate before the exam and during breaks (kind of unusual). Put it all together, the lack of sleep, caffeine, sugar & stress and by the time I got to the verbal section I had a pounding headache. My focus felt just a little bit off, and with about 10-15 minutes left, I couldn't wait to just be done with it, and even though I had plenty of time left I rushed through the last 6-8 verbal questions. The result was a V score about 5-7 points below my average practice scores - actually well lower than any verbal score I had seen in practice.
The second time around, more or less exactly 1 month later, I was well rested, had a better plan about what to eat and drink, and had a sense of calmness during the entire exam. I actually breezed through the verbal section with 20 minutes to spare, my focus was top notch that day and the answers seemed to pop out at me. I think think the key difference between the first and second tries was fatigue at the end of the test as influenced by stress, rest, and chemicals (caffeine, sugar).
So, if your observation about lower verbal breakdowns is correct, it would make sense because verbal is the last part of the exam and most likely to be influenced by test-taker fatigue. It's definitely important to work on endurance when you practice, get as much rest as possible (this may or may not be tough for some), and think about what you eat and drink on test day.
Yeah... I also think AWAs play a role in the fatigue. I did not do the whole AWA in any of my practice tests. I'll jot down points that I would expand on and move on to the next essay/section. On the exam day, I finished the essays with only about 5-10 seconds to spare.