It doesn’t work for me. For example, if I set the language “Prioritize common names used in this place” to France, but keep the language settings as default, the common names show up in English. If I change the locale to French than it does show the common names in French. But that’s not what I would like to do: I want to keep the system language English but show the common names in my local language.
This is on the web interface using Firefox 67.0.1.