There's not much out there on the specifics of Amazon's approach to writing, but there are bits and pieces around.

Jeff Bezos's 2017 shareholder letter highlights some of his thinking around 6-page narratives: https://www.sec.gov/Archives/edgar/data/1018724/000119312518...

This Slab article by Ben Bashaw is pretty good on the topic: https://slab.com/blog/jeff-bezos-writing-management-strategy...

Scott does a good job of some of the major points of Amazon writing based on his time there (this was written based on a previous HN discussion on Amazon writing): https://blog.usejournal.com/writing-docs-at-amazon-e02580861...