Yeah I think the round trip ticket is what ticks CBSA, but logically its a year round open ticket and I do plan to visit my parents at some point especially during the lunar new year period of time.
And yes, airlines are required to check with CBSA before they issue a boarding pass.
I just got my round trip ticket refunded and gonna book a one way ticket instead and give it another go before my COPR expires.
There isn't a clear rule for us, unlike other passengers who are students. They are allowed to travel with school letter stating that the school is starting terms. It just makes it harder for us because we don't really have anything formal other than our COPR.