It is not so much of caste cliques in these groups. As you noticed it yourself, H1-B employees are on-call for everything: if a manager requests something at 7:

It is not so much of caste cliques in these groups. As you noticed it yourself, H1-B employees are on-call for everything: if a manager requests something at 7:24 pm, you can expect a reply from an Indian H1-B by 7:30 pm. Then, there is game of "appearing to work hard". A team with majority of Indians is full of "appearances of working hard". Here are some example of such appearances: (a) reply to emails after work-hours (b) last minute requests to other teams, as though it is urgent, involving managers and others. (c) instead of being upfront, they engage in subtle hard-working techniques. People can add other examples, as they are relevant to study this Indian phenomenon. This phenomenon has less to do with castes, than more to do with the Indian way of 'management' before the British Raj came to India.