This statement - "None of these requests appear to be used for customer features like last read location." - bugs me, because it's fairly obviously false, and detracts from the real concerns. To sync a "last read page" across devices, you need to send a location back to Amazon. It's also appropriate to tie a location to a device, so you can pick the appropriate device to sync your position from. And, when you highlig…
There's no motive on Amazon's part to do it this way, it would be a hassle to implement, possibly not great for battery life, and I expect that users don't care much.
Frankly, I don't care much, in practice. In principle, yes; everything which can be kept private, should be. But Amazon knowing what page I'm on just doesn't discomfit me, the way the prospect of some company being able to read my messages does.