I can't see the foul. The player is already in motion when he starts doing his backflips, so I don't see the false start. And I can't find any place in the rules that mandates that a player in motion must do so without his hands touching the ground.
It is also not a live ball foul for illegal motion, the backflips are done parallel to the LOS, clearly in the backfield, by a player who was not a lineman.
As a supervisor, I'd do the following:
- have a talk with the crew, especially the WH. Not reprimanding, but clearing things up
- ask the coach/AD why they stupidly did not confer with ME beforehand, so I could clear things up with them and my officials before an unpleasant situation occurs. (German: Frag nicht den Schmiedl, frag den Schmied).