If you assume that everyone is rational only based on the points brought up so far and not their individual thoughts on the issue as a whole then it may work that way. But it is still groupthink to go along with the current trend in a conversation just because, highlighted by sudden switches to other good points that you did not see at first because you were too busy agreeing with what was said.
If people just agree with whatever the most recent person to speak up says, then that could be considered groupthink, but accepting that someone has noticed something you didn't and thus your previous opinion was incorrect is not groupthink, it's maturity.