I often get answers in non-english languages. I don't understand why they aren't forcing the language that the user is browsing with unless otherwise specified.
When I was googling something about oil refining equipment it started answering in Arabic, obviously.
I think they’re probably just passing some context on the user (region) and instructing it to use that language. I assume many queries you cannot trace to the user language because they’re just some generic search terms (‘taj mahal’,’Donald Trump China’ or whatever) so they probably instruct the model to answer in a specific language and they overdo it a bit