Right, AWS accounts created before September 2017 are coupled to amazon.com retail accounts. Accounts created after this are separate.
For those of us with coupled accounts, is there any way to separate them?
Change the root user email on your AWS account or the Amazon retail address to something different.
That doesn't work for old accounts. Changing your root email address will also change it for the retail account. This is documented behavior by AWS: https://aws.amazon.com/premiumsupport/knowledge-center/trans...
Perhaps it's because my account is very old - possibly having been created near the inception of AWS. I have no memory of creating the account.