Yep...you'd better be on the ground before it happens
Unfortunately, I think it's almost impossible to say for the rudder just by watching the video...PRIM, SEC's actions or whatever they called it on that one are transparent to the user.
There are only 2 lucky guys who could shed the light.
Am not a mechanical engineer, but one of the reasons could be turn coordination (even for small inputs?), momemtum equilibrium,...even if a rudder seeming to go repetitively from left to right looks strange to me...
We'll find out by flying it...