"The answer is that they didn’t do it by pressing on the accelerator pedal. Instead, Mother Nature found a way to make the engine speed increase while the driver’s foot was off the accelerator pedal and without producing any engine torque, so there was no need for the engine torque to overcome the load caused by the drive train.." (Page 20)
Cool, acceleration with no torque.
The upshot of his theory that the torque controller thinks that the idle controller still has control as a result of 0% pedal (however it ends up in that situation) and does nothing to intervene as a result doesn't seem far-fetched.
Controllers entering the wrong mode for the circumstances is not an unusual thing at all: https://en.wikipedia.org/wiki/TAM_Airlines_Flight_3054, or
http://ccnr.org/fatal_dose.html for a particularly chilling example.