Factual error: At the very end of the movie, the Pope gives the nuns a standing ovation. The other people seated in the box with him should have immediately risen at this time. Instead, the man seated to his left looks up at him, seeing that the pontiff has stood, but makes no movement to join him on his feet.
Factual error: At the end of the movie when they put on the concert for the Pope, Dolores is no longer wearing a full habit as her hair and ears (with big hoop earrings are visible). She isn't wearing a full habit because she would not have been allowed to, especially in the Pope's presence, since it was made public that she's not really a nun. However, during the end credits there is a picture of her with the Pope, and she is wearing a full habit.
Answer: The event wasn't a Mass, it was a concert that the Pope requested. So neither he nor anyone else is there to worship; they're just there to hear the nuns sing.
ksc