When using a scheduler and commenting on a meeting, it is possible to add comments. Those comments are visible to the students. Unless I'm missing something, it is not possible to prevent students from viewing those comments.
I understand the main purpose is for students to get feedback (which I think is vital), but some teachers may want to use it to organise oral exams and add comments online to the exams and make those comments available only after the exam session.
This is probably not a priority, but could come in handy in assessment situations.