I think common sense prevails here. Same reason they have to pull your bags if you decide not to travel, but they don't if something unexpected causes you not to go. If you can't plan on something happening, you can't inculde it in some attack. Now I guess the conspericy theorists would say that maybe he poisoned the CA's drink when he wasn't looking and then sat back and waited hoping that
1. The CA died
2. The FO wanted help
3. There weren't any DH or other pilots on board with more than a PPL
Sounds a bit far fetched.
Agreed that a PPL would probably be more of a hassle than a help, but even if its just taking the radios...beets nothing.
Wonder if the guy logged it.