It's also on Dr. Brady's list of the "mental crutches" used to undermine our recovery from TMS in Pain Free for Life, so I would be inclined to say that it is not true.
WOW totally forgot about that! I remember hearing that when I had back pain.
When I learned about Dr. Sarno and realized nothing physical was causing my pain (not even the herniated discs) I stopped sleeping with the pillow between my knees. In retrospect it seems silly to me to think that would do anything!