This is a journalist with credentials with a fully sourced and referenced book. It is censorship because of Amazon's absolutely dominance over the market. Their marketshare means they literally control the medium for the majority of people in this world who read e-books.
You can say the same thing about Google/Youtube: it's their platform, but when 90% of people in the world go there first for videos, any removal does turn into censorship.
Yes, we should all be running our own peer-tube instances and authors running their own sites to distribute DRM free books, but until we actually get there (and we won't because people are sheep and don't like putting in effort when so much is in front of them on their 1984 distraction device), then Google, Amazon and others will continue to be The Ministry of Truth.
I wrote about this in 2017:
https://battlepenguin.com/politics/the-new-era-of-corporate-...