This is an old post, but I recently discovered the problem and wanted to update it with the solution in case anyone else is searching for it. The problem was actually the dictionary being used. As you can see from the screenshot, "English (United Kingdom, Oxford English Dictionary spelling)" was selected. This does not appear to be an option anymore, so I installed "English (United Kingdom)" instead, and English spellings are now being treated correctly. If you are still using the OED version, I suggest removing it and installing the plain UK dictionary instead.