I don't have a good reference point since it looks like the second KOA-SFO is a 7M9 now, but normally the last 4 seats are not available for any amount of money and not in J inventory. For example, that frame (N221UA) is next flying tomorrow's 2191 EWR-LAX. The flight is booked 28/32 and is J0 with 5 unassigned seats (yes, the extra four seats can be chosen while the frame is assigned).

I'm not 100% confident there isn't something different for certain Hawaii sectors, but KOA-SFO isn't a flight which requires the 77O so I would be mildly surprised.