Friend had a very odd experience waitlist experience this week on SFO-FRA (I followed on the app in real time so this is not a second-hand report). At T-24, he and wife were 1 & 2 on the list with 772 showing booked 46/49. Usual gyrations followed, and by T-1 they had dropped to 3 and 4 with cabin still showing booked 46/49. One of the seats disappeared out of nowhere, then the first two pax on the list cleared and app showed "Full" with friends now 1 & 2 on the list. But the seat map still showed an empty Polaris seat (not 1A). Friend went up to the GA who apparently looked puzzled, but eventually handed him a Polaris BP (for a middle seat towards the rear of the front cabin).

My only possible explanation is that since this was a sub-12 hour flight, they didn't need the pilot rest seat, which left one seat empty. But very odd that availability always showed as 49 and that app showed booked "Full" and yet there was still one open seat (which apparently would have flown empty if he didn't ask the GA about it).