Analyzing log files for duration/pages visited is probably easier than the equivalent for web server logs, and there are very many services that will analyze those for you.
The books currently track by location point and you could log on blocks (e.g. every 100 location points progressed).
Amazon's books are already DRM'd to hell, meaning the kindle has to use the unlimited books through the marketplace. Then it's just a matter of reporting user stats, which can be covered in the Unlimited TOS.
Fast-reading bad actor accounts can be flagged as abusers through pattern recognition. Since a subscription is necessary, creating numerous accounts to game the system becomes expensive fast.
I subscribe to F+SF and it would annoy me if I were technically prevented from skipping the end of stories that don't resonate with me.
Normal people who don't find a book engaging can still skip the end, just that they'll (justifiably) be worth less to the author.
Still, I will agree that that will make scammers' lives harder.
(I'm excluding Kindle Web Viewer, of course. Perhaps it should not have access to Kindle Unlimited.)
That said, Amazon is already syncing your location,and any annotations you've made[1] so they persist across all kindle devices, so there's already a bunch of tracking in place. Given that there's already some tracking, I wouldn't be too opposed to a per-page bit for whether it was read, triggered when the page has been lingered on for five or more seconds (scaled down to 1 second for partial pages, such as ends of chapters).
1: Anyone remember the big episode years back over Amazon realizing they didn't have the license to a book, then removing it from all Kindle devices automatically, including the annotations made? In what is possibly the most ironic situation I can imagine, the book was 1984.
Plus, lots of significant ambiguities to solve: user is reading a page, gets up to do something else, forgets Kindle open. How many minutes do you bill? This might be solvable with the proper signals and rules, but I believe this is far from trivial.
If you're comfortable browsing the internet, this level of reporting on a Kindle seems almost quaint by comparison.
Yeah, I'm not okay with that other tracking either. In addition, I am paying for my Kindle and my Kindle books or KU subscription. It used to be only free services tracked you, but I guess that limitation is coming to an end.
If Amazon doesn't need the exact pages read, POPCNT the total and send that.
but thats still pretty minor
The reason the scam worked is that it encourages all readers to jump to the end of the book (via a link on the first page). I don't think there would be an equivalent way to force people to page through and pause on each page.
So, I don't think "that wouldn't change anything".
You would need to fake the logs for paid accounts, and since rev sharing is a formula of all paid subscriptions, you'd be hard pressed to make positive returns.
