Just a data point. Bought a HND-LAX ticket in main cabin back in June, for a flight in early Sept. Waitlisted. On the day of departure, app showed 1 seat, but it's blocked for whatever reason. Probably crew rest. I checked with agent, all told me business class was full. So I didn't get the upgrade. So now I have 2 SWU going to waste.. I'm thinking of buying a expertflyer subscription to make my life easier. But I bet it'd be impossible to find confirmed space on the 20 seat 788s.