Thing is, Survivor now films both seasons in the same vicinity back-to-back. This current season was unusual in that it was filmed immediately prior to Survivor 31, in order to set up the viewer voted season 31, but that was the exception to their practice these days. I would expect Survivor to go back to filming their fall and then spring season back-to-back for seasons 33-34.
As to TAR, the lead time to prepare the spring cycle is such that the route/task planning and the casting has to be underway before the fall cycle begins airing. That even holds for returning racer seasons as well. That's why I think the renewal was in fact for both 29/20. JMHO. YMMV.