Maybe because in these cases she had nothing to complain about the students. Although I don't think the quality of the images is any different. I also think that the role of a teacher is not just to correct pupils and point them out to mistakes. I think that everyone with a learning process needs some form of reward or appreciation to encourage them and bring more motivation and enthusiasm to their work.
I also think that the role of a teacher is not just to correct pupils and point them out to mistakes.