@Christine615, @Gillian166,
I don't dispute that the place wasn't as clean as it should have been, but the main reason why I would have had declined the guest's last claim and refund request is that her refusal to allow the cleaners return to the rental went against the Air Cover requirement that guests must first allow the host the opportunity to rectify an issue. It seems suspicious to me that a person who seems so well versed with the Air Cover policy would break one of it's primary steps before submitting a claim. I also am not fully convinced that she found the bones on the last night of her stay, and not earlier when she said that they'd cleaned up, but decided to use their discovery as a reason for another refund later on.
The guest stated that she slept in the room during her entire stay ("I’m haunted by the thought that I had been sleeping with bones and who knows what else."). So, the smell wasn't so disturbing that she was unable to sleep, nor did it impact her ability to enjoy her stay ("Minifridge in place, we continued our vacation. I will say here that Montreal is lovely, and we had a great time, other than this last part."). The discovery of the rib bones was gross, but she shouldn't be compensated for something that didn't affect her ability to enjoy the rental, because apparently the overall visible cleanliness and smell of the space was amenable enough that she was able to complete her stay.
This is what I surmised from the TPG article. The guest found the rental to be not to her standards, but didn't want to pay the higher prices for the available spaces that she may have liked better ("Hotel prices were high and last-minute rentals were scarce."). Although there was a dearth of available properties, she thought that Airbnb should put her into another property regardless of the cost, and at no additional cost to her ("The problem was that there was nowhere for us to move to from our current location. Airbnb Support sent a link to properties, many of which had their next availability in January (I was visiting the first week in August).". She had a sense of entitlement, because instead of working with the host to correct the cleaning situation from the beginning, she felt that she should have been upgraded to a space that she was unwilling to pay for or refunded for something that didn't disrupt her stay ("It’s certainly not what I hoped for, asked for or think should have been the final outcome.").