If the language/country pair is found in the database, it is used.
If the language is found but the country is not, or if the country is AnyCountry, the language is used with the most appropriate available country (for example, Germany for German),
If neither the language nor the country are found, QLocale defaults to the default locale (see setDefault()).
Очевидно тут действует третий вариант. А у вас были установлены эти локали?