I have a 2020 QLED and the Apple TV app does indeed play in HDR10+ so my app has been updated.
I checked my QN90A tv again today.
The ATV app version is 13.0 , region is United Kingdom , maybe I should have mentioned that but would have thought roll out would be the same.
It doesn’t seem right that the actual tvOS is 13.0 , it must be 15.0.
Also when it is playing a movie on the app , the info button does not report the signal type.
I have the 2022 ATV 4K and when it is playing hdr10+ Content , the info button reports the signal (as HDR10+) eg with Godzilla vs Kong.