It is logical. When I was in China, my university has international students as well, they also exclusively hang out with only each other. Actually, it is Westerners hang out with Westerners(US/Germany/France, etc you name it), Koreans hang out with Koreans, Japanese hang out with Japanese, and Africans hang out with each other.

Is this really that abnormal? That when exposed to a foreign environment and probably not very good at the language, people just turn to other people that is facing/faced the similar situation before for ... help and support?

When I was a student, I wanted to hang out with the locals' as well, but the cultural difference is pretty obvious: I don't really like partying, couldn't drink too much, grown up with very different music, and often time I didn't get other people's jokes that I felt like an idiot. And since my family paid premium to send me here, I spent most of the time in library studying, by myself or with other Chinese students, just like I did back in college, leaving little time for culture immersion.

So maybe the problem should be, the school should call more people to participate in STEM classes? Or force a diverse study group, that worked well for some of my classes, and I have a good time collaborating with my teammates.