Max,
If the Relief thought he was going to LAX when he was really going to SFO and he was NOT PF, how would his actions (if he actually had to take any) have been different? If he had been retrieving LAX weather (like some idiots do just after takeoff from HKG, and, all the way across the pond, every hour, like it were going to make a difference in the flight) and it was terrible (possibly requiring a diversion) he'd have been thinking about going to SFO anyway!
I know relief guys who don't even LOOK at the paperwork and would be perfectly capable of doing their job properly and safely if and when the sh*t hit the fan.
It's not a f****n' lunar mission!