I think there are some bugs with matching. I have a category commblog, and I could not assign an icon to a commblog-review category. I ended up working around it by calling it community-blog-review instead. (The match / partial config didn’t seem to help, but maybe I was doing that wrong.)
Honestly, ideally, instead of the kind of klunky table-based config, it’d be really nice if this could be set on the actual config page for each category. I understand that’s probably not possible (or at least, not easy!) with a theme component, though.