Hi! I have been told by many people in India and one from the US. Indians were denied boarding by the ALO at YYZ and they communicated it to the airline officials. And the person from the US wasn't stopped by the airlines and landed in canada. She was then detained by the CBSA and her passport was taken away. She was then flown back to South Carolina. Another person who wasn't a first time flier told people that immigration officer told her that, " Being a student doesn't give you the right to travel at any time, and certainly, not at a time like this" . The officer also refuted the information given by IRCC that students approved before 18 march can travel.
Its IRCC which hasn't communicated the rules either to students or to CBSA. And, as a result, students are ending up being denied entry or flown back to their origin place.
Hope that they will update the instructions and not misguide people with rules that are not in force or if ever were.