A little silly for your customer to cancel because of this - as airbnb makes it clear in all publicity that full payment is due on booking for late bookings and split payment available for bookings made some time in advance @Kk5
Never had a guest have a problem with it with four years experience and hundreds of guests.
You have to wonder why a guest would go though the effort of making a booking, paying in full and then going to the effort of cancelling it? Sounds like you avoided a problem guest.