As a former Kindle developer, I can say that most of what's mentioned in this article are metrics used to understand how the features are used (bookmarks, highlights, dictionnary, etc.), how much they are used, and in which country. This allows the teams to focus on features that are actively used, and sometimes lead to discontinuing features that see little to no use. Hope that helps.
I mean, we already knew this, but it means any and all Amazon hardware must be considered potentially hostile.