Not sure what happened here. Recently took a DCA-IAH-xxx flight.
First, I was super annoyed United refuses to clear down to J2 on DCA-IAH. They never do in my experience. I was #2 on the list at the 24 hour mark up until the 1h mark and the flight moved from J1 to J2 to J4. At J4 it should have cleared #1 and #2. Anyway...
At T-1h somebody jumps the queue and is #1 (likely a rebook but who knows). Flight is 16/15/13 (cap/booked/checked in). I'm now #3.
At T-40m when boarding starts #2 is cleared into the unbooked seat. She takes it. I take my economy seat.
At T-30m on the mark when the other two failed to check-in #1 and #2 (now me) get cleared. However, based on the upgrade list I got the upgrade before #1 did. I still don't know #1s status as he sat a few rows behind me.
The only other time I've seen #1 skipped over the upgrade list is when they are waitlisted for "P" (e.g. bought first on another flight and are standing by on an earlier one). But it doesn't explain why they would have been skipped definitely once and possibly twice. This was a revenue pax, not NRSA.
-RM