Originally Posted by tracon

This sentence makes no sense.

If the medical was on the inbound, it's possible that there wasn't enough supplies(ie: O2) to operate the flight back.
If new medical supplies couldn't be sourced in a timely fashion the crew would have timed out.
That's assuming it's the same crew operating YOW-CUN-YWG. A 12.5 hour duty day if nothing goes wrong.