I read somewhere that during the seder, the participants don't actually have to eat a piece from the top matzo that is distributed to everyone at the table by motzi matzah, rather he can just eat his kezayis (his own separate kezayis that the leader did not make the bracha over) and be done with it. Does anyone know where this piece of information can be found, I've tried to find it again but I was not able to.