Hmm, very interesting information. I love the experimental aspect of it.
Geoff, I do find it interesting when you state "overtraining is a rare medical condition, under-recovering and injuries from fatigue are far more common". Yet in the article you cite, Everyday Training for the Everyday Athelete" Nick Horton states, "overtraining is not a complete fabrication, but it is close to one".
Think of the central nervous system as the central powerplant to a city. It’s a limited pool of energy. If the city gets too big and puts too much strain on a particular powerplant, the power goes out. Fatigue in the central nervous system explains the old, “throw a rock in the pool” effect of whole body movements. This is why you can do a hardcore leg workout today, come in the gym tomorrow, and find that the strength on your bench press is negatively affected. The fatigue in your bench press doesn’t come from muscular fatigue, but through neural fatigue, overtraining.
I like Jeff's idea of planned intensity. This or using a different variation of squat each day makes more sence to me. Going by feel has it's problems. Particularly if this is your first time through such a program.
But it has peaked my curiosity, squat on gentleman.