The problem is when a name is the only name used in a given place, but because that place was not added to the name, people running the site set to a specific place see the default name which is not used in that place.
For example: Gliricidia sepium. The default Spanish name is cacahuananche. Now, in the Dominican Republic, I never hear anyone call it that; everybody I know there calls it piñón. Yet, although I have my language setting set specifically to Dominican Republic, it still appears for me as cacahuananche. This means that I cannot use the language settings to learn the local Dominican names, which was the reason I set them in the first place.
This would be a solvable problem if I could add the place Dominican Republic to the name piñón, which is already present as a non-default Spanish name.