I designed this. I won't speak to any past or current practices, but I will say this: Amazon is obsessive about protecting customer privacy.
Note: I am the author of the article above.
For me, it comes down to alignment and value. Amazon stands to lose a lot if they decided to suddenly stop caring about customers, or not take security seriously. And the Internet gets pretty small if your threat model requires zero trust.
Does "privacy" mean Amazon will spy on their customers, but won't share that data further?