This has also happened to my listing today (I am a superhost in Sydney who has been on Airbnb almost 4 years). A call to support confirmed that yes, this '100% refundable' is their new policy, although I cannot recall any notification of this happening.
Now there is NO disincentive for guests to cancel, and with my policy set at Moderate this could happen up to 5 days ahead. This is not acceptable, and I have immediately changed my cancellation policy to Strict - which I suspect will reduce my bookings, the opposite effect to what Airbnb is hoping.
Other platforms such as Stayz and Tripadvisor do not support such policies, and their standard policy is to take a deposit that is forfeited in the case of cancellation. I will certainly be prioritising my listing on these platforms now.