The OP says he is "a security conscious user who follows the best practices like: using unique passwords, 2FA, only using a secure computer and being able to spot phishing attacks from a mile away..." yet I do not think he enabled 2FA on Amazon.com. If he did customer service would not have helped the hacker pretending to be him. As their help page says, "If you need help from Customer Service after enabling Two-Step…
Interestingly, last night I did get an SMS: "Message from Amazon Customer Service: xxxxx is your Amazon security code" even though my 2FA is not an SMS (it's using authenticator).
I don't have access to the recording, so I have no idea what actually happened. But based on the email ("here's the details" on your order) I'm almost certain they were successful. Probably just told them that they lost the phone, or something. At this point, they've now been able to get almost everything possible about me.
Also interestingly, not once did Amazon recommend that I use 2FA to avoid social engineering. I was told by two different support reps to change my password though.