Amazon’s Privacy policies, in particular What Personal Information About Customers Does Amazon Collect?:
https://www.amazon.com/gp/help/custo...deId=201909010
‘Usage’ data such as that the article enumerates, is obviously in part needed to sync reading position across devices, a feature that most users expect. They may also be preparing to add features that would present more granular reading statistics (something I have a mild interest in).
It would be illuminating had the writer turned off sync feature to see what that changes about the data that gets sent to Amazon. And if possible, compare with behavior on Kindle apps for Fire/Android/iOS.
None of the information collected includes ‘personal identifiers’, none of which exist locally on the Kindle. I’m all in favor of collecting data to discover issues, and improve features and services, as long as it doesn’t compromise privacy (which this doesn’t appear to do).