FWIW, my initial - non conspiratorial - take on the events is:
The pilot's training regime was poorly thought-out in parts. The aspects relating to handling wake turbulence appear to exaggerate the effects, and encourage the pilot to respond quicker and harder than necessary.
This is coupled with unclear/misguided directions wrt rudder, and some missunderstanding.
The effects of the actual wake turbulence, which are impossible to accurately recreate may have been coincidentally reinforcing...
I'm no expert on wake turbulence, but, for the sake of imagery, imagine a boat encountering waves (parallel rather than perpendicular to travel) - the immediate effect is in one direction, then cresting the wave, in the other. If the pilot has commenced reacting to the first input, the second could reinforce the correction. If this was then followed by a second larger "wave", then the harmonics/sympathetic response would be significantly increased.
In such a scenario, once the pilot is preoccupied with the rudder and unexpected feedbacks, would such an outcome not be possible?
Feel free to shoot this down in flames! I'll admit I've only briefly looked over the report, etc.