[lxgr]

This used to be true for Windows, but I don't think it is anymore. At least on the last version I used, I was able to change the UI language (but that was also marketed as an "Ultimate Edition perk" or something similar, so I'm not sure if OEM versions are still language-locked).

Where it probably gets tricky is for languages that operating systems are not commonly available in – users presumably have less of an incentive to set the correct locale if it does not make an immediate difference (assuming it is even offered in the setup dialog).