Updating Inbox Apps or switching the language of Inbox Apps to installed Language Packs requires machines to have access to Microsoft Store. Clients in areas that do not allow any internet connection (e.g. regulatory limitation) cannot update or switch the language.
Since Microsoft is using DOD running completely in Windows 10 as a showcase, I am always wondering if all DOD machines have Microsoft Store access.
If Configuration Manager would host and update the sources for the Inbox Apps incl. language files, we could also participate from the content delivery optimizations.