[fjtorres]

Amazon reading tracking is no secret; never has been.
Whispersync has always done it, from day one--it is necessary to synchronize across devices.
Kindle readers track average reading speed and time spent on a page in order to estimate reading time left to finish a chapter.
They probably also track things like books finished vs books abandoned, time between purchases, percent conversion of samples to purchases and a whole bunch more things.
Some things, that feed into user-friendly features, are tied to your account. Most are lumped in anonymously with the data from the other 50million kindle accounts.

Staying offline doesn't help much--the data is locally cached and uploaded at sync time.
Now, if you only sideload, never activate wifi, and don't mind missing out on a bunch of features, you can still protect your reading privacy. But not your purchasing habits, which is what Amazon really cares about.
To deny them that, you have to never do business with them.
Which is fine by them.

As for the 10% mark for payment? Kindle book free samples feature the first 10%, so it makes sense to count checkouts abandoned that quickly as samples. The other subscription services do the same, though their payout policies are different.

Some tracking is always needed to make things work.
If it bothers you, then move along...move along...