If you attack and get lots of covers/assist/caps and get a lot of flag kills, flag returns, and last second saves at the same time the team balancer will cripple you because you can get so many points making it think you are a lot stronger then you actually are, if you don't want unbalanced games towards you have to be tactical like only killing at certain times or avoid getting lots of covers or flag kills/returns to avoid getting more points that's why you see people holding back.