Andrew, not tagging you here as the current glitches seem then to remove the text from the post...
I started hosting in my current house in 2016 and have had hundreds of guests stay here. Aside from 2020, when there were tonnes of COVID cancellations, I don't believe I've ever had a guest who cancelled for extenuating circumstances (only cancelled and got refunded within the boundaries of the cancellation policy).
I do remember a guest trying to get a full refund (she already got a partial one) for a last minute cancellation, claiming her grandmother had died. However, there was something in the correspondence and in her attitude that just didn't ring true. She really tried to pressurise me. I just told her she needed to apply to Airbnb for extenuating circumstances (sending her a link to the policy) and that was the put an end to the harassment.