I think the GA followed the policy and I don't feel that it needs review. First, employee upgrades is a benefit of their employment. At the rate they are paid that seems to be a fair perk.
I think if they started giving them away to every elite that asked than no elites would buy them and the revenue to the company would drop not improve.
I don't feel that the OP was treated unfairly at all. I would also be willing to bet that there were other PE and GE sitting in the back. IF the policy was to give free U/G on intl flights on a space available at the gate I am not sure that a GE would have much of a chance anyway. Since the PE and their companions would be eligible first.