Netflix's video streams are delivered from devices installed at ISPs.

Their most valuable data: what is being watched, where, by whom, is hidden from Amazon.

Not always. The devices at the ISPs are basically a local cache. They don’t have devices at every ISP and all of their content isn’t on every device.

But that’s really neither here nor there. I doubt very seriously that even if Amazon (AWS not the retail side) was snooping on customer data - which I believe they would be fool to do so - they couldn’t inspect the video stream to know what was playing where.

Encryption doesn't hide everything. For example, Amazon could estimate the geographical location of everyone watching Netflix and use that information to determine optimal billboard advertisement locations for it's advertisement campaign.