I think the way the brazilian players celebrate, usually, has nothing to do with the other teams they're playing against. Paula, Adenizía and Garay yell after a point to push themselves e their teammates harder, to let loose the tention so they can play better, to get the momentum to their side.
And surprises me to see that some people think brazilians had overconfidence, because in many matches they show the complete oposite, they respect too much, that's what bother many brazilian fans: the lacking of confidence of such a good team.