How airlines managed inventory in 2014 and how they do it in 2025 has maybe changed a bit? Once JAL has sold all the standard awards on a flight, and start selling dynamic priced awards, it is unlikely that a cancelled seat will go back in to the standard award pool. This is for J only, but with F you risk that someone has a waitlist request, either for upgrade or award, and a cancelled award would be assigned there before going to the general pool.