That maneuver they were attempting looks WILD. Would have been amazing to have pulled of. Or, perhaps to have regularly pulled off until today. I'm guessing that must be some sort of vectored thrust trickery.
I don't think anything after the second jet's merge was deliberate. NASA's HARV is the only F/A-18 with a thrust vectoring exhaust designed for it, and it's doubtful that similar kit would go on an EW jet.
What's shown in the video appears to be some form of slipstreaming by the chase craft that causes them both to lose pitch authority, pulling up into a stall state and then a yaw tailslide.
They weren’t attempting anything, just repositioning for the next pass. They were flying away from the audience. They lost track of each other.