In fact, it works.
If you search with , Alkaline will also return pages with With (since case-sensitive is not enabled, neither is whole words only). Exclusions are case-sensitive and of course match whole words. Try searching with opt:case opt:whole , this will surely return no results if your dictionary contains with .
Make sure that your indexes were created after the dictionary has been defined. Alkaline will use it only for newly indexed pages.