Ok, I made some progress. I discovered that the exception was due to not having an RVO controller attached to the AI and an RVO sim in the scene. After adding these I could use AIPathAlignedToSurface with some success.
I am having an issue now with the destination setter. My AIs don’t seem to reach the target I’ve given them, especially if it is on the other side of the sphere. In fact, the destination listed in the debug section of AIPathAlignedToSurface is different from the target I put in DestinationSetter. It almost looks like the AIs find a new target that is on the top hemisphere of my surface that is horizontally aligned with the destination when the destination is on the bottom half of the sphere.
Seems similar to the issue posted here: Game object stuck when traveling on spherical surface - #7 by Thompson