I'm surprised to hear about FriendlySkies's friend's luck, too. The rules explicitly state that companions must be on the same flight (and on the same standby reservation) as the "sponsor" -- the employee -- to be eligible for int'l F.

In my brief experience at UA, int'l F was carefully guarded so that only employees and their accompanied companions could standby for it, including when F was wide open. On several occasions, my unaccompanied companions (and, in one case, parents) flew TPAC in Y because there was no availability in C, even when F was relatively empty.

This also applies to spouses/partners/Enrolled Friends traveling with companions. My Enrolled Friend (individual designated to receive partner-equivalent travel benefits by an unmarried/un-partnered employee) made the mistake of questioning a GA when told that he and his companions could not standby for F to PEK because the employee was not traveling as well.

Also, to get pretty technical, I learned that employee-accompanied companions can't fly F if the employee checks in as a BP10 to save the service charge. In that case, the companion drops to BP8C and is treated as unaccompanied. I had to reissue my boarding pass as a BP8A to get my companion an F seat, and the flight left with four seats open in F.