It might just be a coincidence and a psychological bias that you noticed it, but given that it would have a very, very clear economic benefit to Amazon if it were true, we're stuck with these facts:
1.) They have an economic incentive to do so
2.) Only they know how their systems work
3.) Their network traffic is encrypted
4.) They face legal risks and user backlash if caught doing so
Given 2+3, you can't be entirely sure that they aren't doing it. If they deny it, your only recourse is to hope that their cost/benefit calculus considers 4.) to be more costly in terms of dollars.
1.) They have an economic incentive to do so
2.) Only they know how their systems work
3.) Their network traffic is encrypted
4.) They face legal risks and user backlash if caught doing so
Given 2+3, you can't be entirely sure that they aren't doing it. If they deny it, your only recourse is to hope that their cost/benefit calculus considers 4.) to be more costly in terms of dollars.