wouldn’t it have been smart to switch Xiumin and Sehun because Xiumin is close to Luhan and Sehun is close to Kai? I mean, SM wanted to create an image of K/M being tight but CheMin, XiuHan and SeKai stick just as well as HunHan. Another reason is that both Xiumin and Sehun are quiet members so switching them don’t make much difference during interviews. However, I think that if Xiumin got to speak in Korean, he wouldn’t have hold himself back so much. Sehun, on the other hand, generally doesn’t speak much in interviews. So being in a Korean sub unit doesn’t really make a difference for him. Anyway, it’s just my two cents.