Marantz av7706 here connected directly to an Apple TV 4K. Ready Player One, and a bunch of other movies all play Atmos audio just fine through the Apple TV app. Netflix, HBO Max, and Amazon Prime apps all play Atmos audio just fine.
But, I have several purchased movies in my library that will only play in 5.1 audio, with the receiver clearly showing multichannel in. These movies are Top Gun, Gravity and The Martian. All three movies show Dolby Vision, and Dolby Atmos in my library but during playback it’s just 5.1 audio. Oh, and to add insult to injury, Ready Player One is in my iTunes library and it plays with Atmos just fine!
Why does the Apple TV Library play Atmos correctly for some movie, but not others? This is especially concerning when the movie shows it has Atmos, other movies work fine with Atmos, and everything else works fine with Atmos.