> setlocale() requires the ".codebase" in the locale. From the man pages, 
> this is an optional detail.
> 
> I opened a PR for this: lib/25877

The description in nls(7) just specifies the possible lexical form of
a locale name.
setlocale() is not bad even if it does not accept such omitted form
for a language, because such form is not available for all languages.

(I do not prefer such ommited form because of ambiguousness...)

--
Takuya SHIOZAKI