@Bob297 Cancelled flights do not fall under the extenuating circumstances policy.
I don't understand you saying the guest is arriving "soon", then you say in 30 days.
From what it sounds like, the guest did squeak in just in time for a full refund- cancelled 30 days before check-in. So the EC policy is irrelevant. The guest will get a full refund minus the Airbnb service fee, which they will retain.
And just because the guest's Air Canada flight was cancelled doesn't mean they couldn't find another flight.