Through their reply we can know: they currently don't accept bitcoin payments, but in the near future, this situation maybe change, isn't it?
You are getting the wrong impression. This isn't about them taking Bitcoion, it's about them paying the book publishers via Bitcoin.
I wonder if there is a processor (e.g. Bitpay and Coinbase) out there who can help them do this.
Screenshot given. If in doubt go contact them. kdp.amazon.com. If you have an Amazon account go here and ask the question:
https://kdp.amazon.com/contact-ushttp://i61.tinypic.com/174gmp.jpg