Clearly they are just trying to force Visa to cut them a deal for reduced fees.
We will have to see how it goes!
In the meantime, Curve might be a good solution for customers caught by this (although it would mean no Section 75 protection for larger purchases).
If you really want to use a Visa credit card, it will allow you to!
Until Visa or your bank pulls an Amex, or the customer support goes AWOL…
Wouldn’t surprise me if Amazon have been strong arming all the issuers down to zero or negligible fees for a while and Visa decided to try and get them on standard terms.