[This is Julia, the OC] I agree, and have many times thought back to why I didn't feel comfortable just claiming a partner for the project. I remember I was doing something else and happened to notice that a few people had posted and been claimed, and that made me insecure, wondering why no one had claimed me.
I think it's more natural to work closely with someone of your same gender, at least when they're a stranger. I'm not blaming men (or women) for that - I'm just describing how that can lead to unintentional exclusion, which is particularly painful for students who values inclusion a lot.