Hi zmclearan,
Thank you. I was able to contact Amazon's first line of support and they said they would escalate this to the development team for the Apple TV Prime video app. This is not a new issue and I've seen it on both the 1080p Apple TV as well as the current generation 4K Apple TV. What's weird is that the UI for the Prime Video app for non-Fire TV devices looks the same across all of these devices (Xbox One X, Nvidia Shield, Roku, Apple TV). However, the quality of streaming on the Fire TV versus non-Apple TV devices is the same (even though the UI looks better on the Fire TV). I am using the newest Fire TV cube that came out a month or so ago and the quality is so much better than using the Amazon app on Apple TV 4K. I am not sure why this is happening and whether Amazon views Apple TV as more of a threat than the other device manufacturers. So, maybe they don't want you to watch the Prime Video App on Apple TV 4K!! The grainier/noisier quality I see on the Prime Video App on Apple TV is not just for Prime Video content but also for Amazon Prime channels like HBO, Showtime, etc..
I am not confident Amazon will do anything to fix this streaming quality issue with the Apple TV. I've reported it to them at least 3-4 times and have to believe many others have as well. I suppose a lot of people who only use one streamer aren't even aware that they are not getting the highest quality streaming from the Prime Video app they can actually get.
