Ticketed EWR-SAN on 12/30 in JN class on the 752, but unable to select a seat. Cabin is booked 15/16 and 4A and 4B are showing missing in the flight status seat map (showing selected / grey on the reservation seat selection page). When I booked, the agent said two seats are blocked and will be released at T-24. Are crew rest seats required on transcons? If not, why block the seats? Risk of downgrade?

Thanks