For this case, the solo aircraft is flying at a lower AOA than the others, it is still developing a vortex sheet roll-up off the wing TE that entrains towards the tip vortices, with a mixing flow in the center from the engine exhaust that is relatively irrotational, but with buckets of turbulence all of its lonesome. The #3 aircraft when they pull the data will find that most of the motion will follow the pilot's inputs; it is going to be a PIO related to the perturbation in a tight tracking task. That's not a criticism of the pilot, the lag in detection, and cognition/recognition response will lead to an opportunity to have a gain and phase issue to the aircraft state. I think the guy actually did well. The error here is to do the Tom Cruise bit, particularly without the music etc. The initial upset is not a large perturbation, the plane follows the controls, which is what the debrief should note, and then avoid such a maneuver.
The tip vortex development over time is pretty well understood, the guys below the fast mover's flight path were quite likely to have a wake encounter, it is just a matter of time. Given more time, the loss of rotational velocity of the vortex results eventually in a point of instability that will cause precession of the vortex, and it kind of does a series of gyroscopic wild rides, stepping out of line laterally, then vertically, describing a square loop, until it finally bursts. Before that, self-excitation in the form of crow instability will occur on aircraft without a centerline jet wake, although if AOA is high enough the jet wake is below the tip vortex and instability can be seen.
The manoeuver is a good way to end up with one pilot becoming a near ace in the one flight without firing a shot.