Ah yes - looks like we group all Xbox models in our reports as "Xbox One". That's annoying. Your Amazon Fire device was served the exact same stream as your Google TV (it's the same app with the same player).
Just wanted to follow up on this and say that unless you specifically select HDR on the Google TV, you won’t get the HDR stream. I have my preference set to Dolby Vision and although it says it will pick up HDR content as well, it only took the 4K SDR stream. When I changed the setting the HDR kicked in.