To be honest, I'm actually in favor of them not needlessly struggling to communicate with each other in broken English. I was once in an Econ class with a Chinese professor that spoke mandarin natively. As did a slim majority of the class. I recall him trying to explain something to the other mandarin-speakers and struggling before squeezing in like a 4 second mandarin quip and the response was a wave of "eureka!" across the other ones. Like he just somehow squeezed the past 40 minutes into 4 seconds and they all finally understood it completely. Astonishingly, really.

"chances are they’ll converse in their native language from time to time"

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...

Agreed, I'm Indian and thus often it is the case that other Indians try to speak with me in Hindi, but I end up having to insist on English in certain contexts.

It's unnecessarily rude and exclusionary towards others. 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.

That's caused by a lack of diversity. If they were from different countries, they would behave differently.