Okay, so then the explanation is that this has nothing to do with EUA, right? Instruments => status is irrelevant, and there's nothing odd about a Gold being ahead of a Plat... Nothing to see here, moving on...
Gold before Plat - correct. Someone between us on the waitlist is a glitch I'm told. As we were both waitlisted using the same instrument, same fare class, same check-in time, (sequential sequence numbers) etc., it should not have been possible for someone to be between us on the upgrade list.