Fascinating stuff. Though I know nothing about Systema, I have experienced similar ideas in other martial arts and taiji teachers -- good and bad -- over the years. The truth of why such methods sometimes work dramatically lies somewhere in the human mind and soul. If we call it autosuggestion or self-hypnosis, then both are often used in the martial arts and can produce scary results in some practitioners in terms of increasing ferocity and resistance to pain and for others just turn them into victims to be drained by unscrupulous teachers.
I think one of the most important things to remember is that the really impressive examples of this kind of training are usually found in teachers who have done a lot of fighting in their lives and/or who have had to control others in their daily occupations. What they can do martially is often the underpinning of their psychological ability to control students or the "susceptible" in their workshops. If they were pushed, they would have the experience of "eating bitter" to back-up the psychological skills whereas the average younger, student who buys the workshops, books and dvds just doesn't have the same experience or martial potential.
Still, interesting stuff and its too bad it so quickly gets wrapped in bullshit by so many teachers when they are seduced by the money to be made from exploiting the overly-gullible.