You sure you figured it out? In theory, it sound like the correct functionality of that feature.
I think maybe the labeling is confusing? The feature tries to filter any listings on the resulting page by the selected category. In addition, it outlines any sub categories that it finds. When there are no sub categories, it says so.
I’m not sure if i addressed your situation, but just wanted to put that out there for anyone reading.
BePro Software Team