DD11's count is at 3: public / magnet / homeschool. But if you think about it, homeschool supports switching things up all the time. One year you could be in a co-op with the same group of kids, that summer you're at science camp for 3 weeks, then you switch it up and get tutored for math and join a writer's group.
My daughter doesn't deal well with change (when she was little she hated anything in her environment changing), but she deals with a bad educational environment even less well. She always made friends, but also felt different and isolated -- I don't think the changes made that worse or better.
I'm sad that she can't have the educational experience she wants (walking to school with her friends, continuity from year to year) but the emotional effects of the lack of appropriate education were so much worse for her.
As for the study, I don't know that you can extrapolate the experience of children in different cultures. There are cultures where continuity, tradition, and local networks are prized a lot higher than here in the US. The experience of moving and changing schools would be very different in these cultures as well.