[Fastera]

Amazon has the ability to record the serial number. I have not SEd iPhone however I did an Apple Watch S5 and in my case whoever put the SN information got it wrong. The SN that was listed in my order details was different to what was on the product/box. That meant that even if they wanted to block it (via Apple) they couldn't.

I have read that they can be locked if the information is given to Apple though I have no personal experience.