Do you have a source for that?
Here are a couple. The first is about results, read the first paragraph...
Mark Allen Interview: A look back at working with Phil Maffetone and what it means for today's triathlete. - Dr. Phil Maffetone
There is some stuff here at the end. Substitute "improving capillary density" for "aerobic base."
Joe Friel - Mark Allens Training
For a visual, think of chicken dinners. Chickens don't fly too much, but they walk around a lot. Building a base is turning white into dark by changing the capillary density. You have to farm capillaries, and encourage them. you can't throw acid all over them. Or maybe make blood pressure too high - they are baby capillaries after all.
Once the capillaries are there, the defensive players will respond the way Pruitt wants and expects them to.
Here is the important part of the narrative:
"I came from a swimming background, which in the 70�s and 80�s when I competed was a sport that lived by the �No Pain, No Gain� motto. My coach would give us workouts that were designed to push us to our limit every single day. I would go home dead, sleep as much as I could, then come back the next day for another round of punishing interval sets.
It was all I knew. So, when I entered the sport of triathlon in the early 1980�s, my mentality was to go as hard as I could at some point in every single workout I did. And to gauge how fast that might have to be, I looked at how fast the best triathletes were running at the end of the short distance races. Guys like Dave Scott, Scott Tinley and Scott Molina were able to hold close to 5 minute miles for their 10ks after swimming and biking!
So that�s what I did. Every run, even the slow ones, for at least one mile, I would try to get close to 5 minute pace. And it worked�sort of. I had some good races the first year or two, but I also suffered from minor injuries and was always feeling one run away from being too burned out to want to continue with my training."
http://www.schfma.org/PDFs/2016_AI/6_2016_AI_Eskew_Mark_Allenon_Heart_Rate_Training.pdf