SWU upgrades come from a completely different bucket than the seats released to an NRSA. SWU upgrades are processed and allocated based on revenue managements willingness to release seats whereas NRSA dont get on to the plane unless those seats arent occupied.

The ATL-JNB run has been extremely full since the World Cup started and I would expect that you havent seen many people scoring the upgrades via SWU during that period because a majority of J seats have been sold.