I think you're correct that this is only valid in root mode. I'll fix that by checking numBoundSamples as well, rather than visiting all the locations. Lucio seemed to think numBoundSamples was the best indicator of movement down in the hierarchy.

As I understood it, SceneInterface::scene( [] ) returns the very top level. In this use, my scene variable may not be at the top (when the user sets the parm) and scene->scene( rootPath ) is just a silly shortcut to get me back to the top level so I can check the boundSamples of the whole hierarchy.