Yup an old thread indeed.
As stated plenty on this forum, I think that the ball is in Amazon's court, they could choose not to offer any payment for paid content through the app, and thus not have to share any revenue on the paid content with Apple and instead ask users to make a purchase from the website, just like every other streaming service. And then separately fight it out with Apple if they want to include the payment portal through the app, while still providing streaming for their customers using ATV.
And I squeezed out yet another refund $20 from Amazon, it's not the dollar amount, but the principle of discriminating against customers who have Apple TV instead of Fire TV. The app exists on iOS, all that needs to be done is porting to tvOS.
The value of the Prime Video content differs by the customer, someone might value shipping cost, while someone else might value Music more and someone might value Prime Video equally. So there is no discussion for me to be had there.