My family and I just flew in F and J longhaul between USA-Tokyo and vice versa (transiting) and J was 100% full on the return flight. F had only 2 seats empty. They ran out of the western set option in J when I tried ordering it 2.5 hours before landing. I assume they have enough for everyone in F, but you can always let your FA know ahead of time to reserve one for you. (Luckily my DH didn't want his in F, so he had his sent to me in J - it was the same pre-landing meal.)