Bobby and Yunhyeong are friendlier because they are sociable, a result of normal teen years spent hanging out with friends outside YG. BI and June entered and stayed in showbiz really early, so it kinda explains why they are a bit socially inept. Donghyuk and Jinhwan are the introvert types, silent but actually are in deep thought of what they should say. All in all, it was their first encounter but I have no doubt they will bond with the newbies later on anyways, Team B boys are quite easygoing with those who reciprocate their playful manners. 

I just read this in the Youtube comment section of Mix&Match episode 1 (bruh I've rewatched it already like 5 times #nolife) and tbh, I do agree. Idk it just amazed me a little-