Wasn't sure where would be best to post this.
But it seems to be that you can't download 4K iTunes movies.
From Apple:
"You can download a local copy of an HD movie, and you might be able to download HDR and Dolby Vision versions, but you can't download a 4K version."
https://support.apple.com/en-us/HT207949
Also does this mean you can't play on macOS either?
From Apple:
“Only the Apple TV 4K, connected to a 4K-compatible television with a compatible ultra-high speed HDMI cable, can play 4K content.”
But it seems to be that you can't download 4K iTunes movies.
From Apple:
"You can download a local copy of an HD movie, and you might be able to download HDR and Dolby Vision versions, but you can't download a 4K version."
https://support.apple.com/en-us/HT207949
Also does this mean you can't play on macOS either?
From Apple:
“Only the Apple TV 4K, connected to a 4K-compatible television with a compatible ultra-high speed HDMI cable, can play 4K content.”