@Nori2
Korean bookings have their own Cancellation rule. Why it is like this I don't know.
However, Airbnb inform Hosts of special Korean circumstances with a message in a Reservation Request. [I don't do Instant Book, but I expect it's the same].
Airbnb message informs of this unique Korean situation and states that Hosts do not have to accept and will not be penalized for declining Korean bookings.
Consequently, it's unlikely Koreans 'abuse' the rule. They simply exercise their right to the rule!
I get quite a few bookings from Koreans. I always hesitate when receiving this special message from Airbnb with Korean Reservation Request.
.
But to date I've accepted virtually all of them, and so far not one has Cancelled.
Maybe it's the luck of the draw.
However, I can only reiterate that I don't do Instant Book. It means I do all I can during Inquiry to satisfy myself of Guests reason for coming to London.