"Failure to anticipate" I do agree that is a factor, however, once full right pedal is applied too quickly and that aircraft is spinning, maintaining full right pedal may not stop the yaw. Under normal circumstances, air only flows in one direction through the fenestron, I suspect that once full pitch is applied quickly, we are asking too much of the fenestron and it can no longer cope (stalled), possibly even allowing air to flow in the wrong direction. One possible solution would be to unstall it with left pedal and re-apply gently......try doing that when spinning to the left at a very disorientating rate and no yaw control.
As always, from the comfort of an armchair, it is very easy to spout "mishandling", "it doesn't exist", but when out of control and applying full pedal to correct with no response, it does exist, something has gone wrong down the back and if it isn't mechanical then it must be aerodynamic (fenestron stall/LTE...call it whatever we like).