I think the search filter called "Region" in CM is looking up category-region, not Kind. This doesn't really cut it, because category-region is a free and often thoughtless choice by creators, whereas Kind region is quite specific to the particular class of asset I'm looking for.
Speaking of class, there is category-class (supposed to be "YX" for Kind region assets) but CM doesn't seem to use that tag either, probably because it also doesn't guarantee anything.
The only way I found to get at Kind region assets was to filter on "Download Station" or "Installed", then sort the resulting list by the heading "Type". Manually scroll down until it comes to Region assets. Presumably CM must be using Kind, but calling it Type.
Personally, I think Kind Regions deserve to be searchable under the Category filter just like everything else.