They should really call it the 'perchance, maybe, imaginable, we'll-see-how-the-staff-feel-on-the-day, possibility of an upgrade' benefit of being a PC member.
I've been PC for the last couple of years and I have to say most stations are pretty good at giving some sort of upgrade, especially the airports, but to call it a guarantee is just a flat out lie when it's absolutely nothing of the sort.