I am Korean, and my language settings are also set to Korean. I was keping track of nearly every snapshot, and I was well aware of the Narrator, which narrated only English. Now that 1.12 is released, I've tried to change the narrator language, but I couldn't. I'm not sure if the language for the game not synchronizing to the narrator's language is a bug, but what I'm sure is that there's no option for language selection.
The narrator is depending on your system language, as minecraft just uses the system's narrator.