That's actually an interesting point. Indeed, how works internalization for Irish, for example? I mean some big international app, like Windows or something. I don't think it's trivial to customize some internal "yes/no" dialog in Windows to use different words for every question, but only for some languages.
It probably helps that dialogs usually use "ok"/"cancel" rather than "yes"/"no". Chinese, for example, doesn't really have a word for "yes", but it does have a word/phrase meaning basically "ok" ("好的"), which is what's used on windows for those dialogs.