This is going way off-topic and should maybe move to a separate thread.
I'll refer you to to this
Kindle Unlimited Royalties page.
- Books only eligible for royalties based on number of pages read (for the first time). Obviously this tracking can only be done if you're reading through Kindle apps. And I assume scrolling too fast or jumping around won't cut it.
- Like other subscription services like Spotify, Netflix, I would assume that the publishers/authors are getting the shorter end of the stick, and it's more profitable for them if you actually buy the book.