While it appears to be good enough in the default situation it becomes an annoyance if/when Tuleap starts supporting other locales because this kind of things are not easy to track afterwards.
Furthermore it's a problem we already have solved in the Tuleap codebase via dynamic loading we should not go back to something less flexible.

On a side note, in this specific case it's a bit better to load only the needed locale data as it reduces the size of the code that need to be loaded by the client.