When a training stimulus is applied, the stress results in an immediate decrease in fitness. After this initial decrease, as the body recovers and adapts, the fitness level increases. Excessive stimuli may depress the fitness level too much, compromising the quality of the supercompensation.
I am by no means saying that Rupp performing a 4xmile workout after a race is the wrong decision. I am just trying to figure out, physiologically, how it fits in the big picture. Is a non-PR attempt race such that his body has the room for more work?