How does this work? Does it just set the synced language and keyboard settings if they are available, or does it actually install them? Because I can sort of see the point of the latter. If I somehow end up in, I don't know, Korea, and find a Windows 8 PC, it'd be pretty neat if I could switch between English and Dutch input languages without having to configure them first.
Input languages don't require anything to be installed anymore, they haven't since Vista. All language versions of Windows support display and input of all the languages that Windows can support. So yeah, if you log in to this hypothetical Korean PC using your Microsoft Account it should be able to have Dutch and English input languages.
UI language is a different kettle of fish entirely, however.