@Fiona274 The Extenuating Circumstances clause has always been in the terms of service, and it has always given Airbnb broad latitude to override cancellation policies at its discretion. I see a lot of people making the case that Airbnb has unlawfully changed the terms of a contract after the sale, but I don't think a close reading of the pre-Covid19 policy supports this.
That's the gamble a host takes with Airbnb. Not only can they override your cancellation policies at any time; they can also cancel any booking, suspend any listing, or delete any user's account at any time without any prior notice or explanation, and it's all right there in the fine print. Another thing that's in the terms of service that all users agree to is paragraph 19:11, waiving the right to participate in a class-action suit.
Whether a specific law was violated would surely vary from country to country, but as far as I can tell as a non-expert, this is more of an ethical issue than a legal one. I don't think Airbnb was playing fair by encouraging guests to demand full refunds that they might not have otherwise sought.