It looks to me like the wbond Package Manager has problems marking ST3-compatible packages as such. Some of the issues may be due to the package makers themselves and their metadata, but not all of the problems.
First, a package listing. Note how all of them only claim to support ST2 - both via the occasional ST2 tag, and in the package description:
http://i.imgur.com/jRqW8bd.png
But, clicking into a package reveals an “ST2/ST3” tag which wasn’t shown on the index page. Plus, conflicting compatibility information in the metadata: