Perhaps they think rehiring and training people for the show is worth it for that extra capacity. Besides, maybe they can use those same show workers for whatever show is going there for HHN?
After the Summer season, the show will be operating on weekends only. If they were to shut down the SES show after HHN for the new coaster, I think they still will have gotten enough “mileage” out of the rehired staff before tearing it down.