@Adam1554 The Extenuating Circumstances policy for Covid is long overdue for an update, but as of now it's not based on your specific country's requirements. Complicating matters further, all of your confirmed bookings are subject to the policy in place at the time they booked, even if they're for next year.
The CDC still recommends that people stay home and isolate for 5 days after testing positive, regardless of vaccination status. Airbnb may well be wary of being the villain in a media narrative about how infected travelers were "forced" to proceed with a stay in someone's home because they couldn't get a refund. Until there's some global consensus that it's OK to travel with Covid, I don't see Airbnb deferring to the whimsical strategies of the British government.