It doesn't? The archive he links to includes a copy of the whitepaper, but this repo is one archivist's collection of files, not an official distribution. The whitepaper is not in the nov08 distribution or the bitcoin-0.1.0.tgz, and the document doesn't include a license statement. I'd believe it's MIT licensed, but this post doesn't establish that fact or sound like he presented more compelling support of the idea to Amazon.
As a practical matter, it's vanishingly unlikely that Satoshi Nakamoto is going to file suit. But as a legal matter, he hasn't shown that the whitepaper was released under a license permitting redistribution or that he has permission from the author. Amazon gave him several options and opportunities, then declined to participate in apparent copyright infringement.
Amazon has a huge problem with people republishing others' books via KDP and their marketplace, even getting fake versions added to or replacing authentic listings. This process seems like it might be a pretty good way of addressing that. The inconvenience comes from not wanting to give the well-practiced scammers a guide to defeating the process, which is a common tradeoff.