I clearly recall reading that there was an instructor in the RHS on that TG stunt.
Anyway, I would expect that the producer would have contractually required the stunt to be made, which means the PIC must have a CPL.
One obvious way around this would be for the actor to be self employed (aren't most actors self employed anyway?), the producer contracts with the actor's company to produce the stunt "somehow", and if the actor's company freely chooses to use the actor to fly the plane (rather than hiring in somebody else) then that should still be doable under a PPL. The key, AIUI, is that the actor is not directly contractually required to fly. It may be that the actor's company is a one man band but the legal separation remains.