That said, that same group often faces exclusion in the wider company (and coming together is often in reaction to that), so it’s kind of miserable for everyone.
This needs to be a big No No. Everyone should speak the language everyone else can understand in the workplace at all times. I natively speak German, but I never speak German at work even when I temporarily was only working with someone visiting from Germany. It would have been rude to everyone around us. But then I'm also weird in that I dislike speaking my native language...
It's unnecessarily rude and exclusionary towards others to speak a language others cannot understand in an environment where they have an interest in participating. All it does is form cliques and encourages toxic dynamics to form.
But on the other hand, I previously encountered the opinion that people who insist on speaking in English (especially without the "quirks" and accent of Indian English) despite being able to do Hindi are just trying to be pretentious.