@sami - i'm not sure I follow all of the details on the facebook post here (it seems to me there are some errors in there but likely of no consequence).
I think unfortunately there are only two things that can be said about this case:
1) For those travelling to Canada by air,
what the airlines think can be a real, practical problem for those trying to travel - especially in covid times. If all of the above is true at least on the important points, I
think it is a case of manifest error - the airline was clearly mistaken in believing that the requirement is that a PR cannot be out of Canada for more than 730 days. Unfortunately this is not always easy to show.
2) What the airline
should have done is both check carefully the requirements
and contacted IRCC/CBSA to confirm that they are allowed to board the airline (as admissible to Canada). Also the travellers
should have checked carefully with the airline beforehand - frankly it's not surprising that the check-in agents do not always know what they're talking about and they tend to be punished for mistakes rather than rewarded for correct decisions (it costs the airline real money if they let someone board who is not entitled to).
3) More knowledgeable members here may wish to comment, but: I think the airline was even more wrong than indicated here. By Canadian law, (I think) any PR with a valid PR card should be allowed to enter Canada (and also to board a plane) and will not be denied entry at the border. Upon examination (i.e. at the border) can start the formal process to show that the PR is not in compliance with the residency obligation and (after appeals, review, etc., etc)
potentially revoke the PR status - but that's not the airline's concern, and while the process goes on, the individual will be allowed into Canada. Or briefly: a PR card that's still valid (by date) should be sufficient for a PR to board a flight to Canada.
But: I'm assuming the info above from the person who had the problem is all correct. Airlines screw up, it does happen. But also, internet versions of what happened are not always correct.
I think you can see hwere the recommendations for you lead here: check with the airline before.
(And as a side note, it's probably obvious, but some airlines and staff at some airports are better informed than others - I doubt this would have occurred with an Air Canada flight from Frankfurt - a big hub for Air Canada from much of Eurasia - for example).