Some owners of the new Apple TV 4K are being told in third-party streaming apps that they are receiving HD video instead of 4K. It remains unclear why.
A series of threads on Reddit and in the Apple support forums show that users are seeing an HD label instead of a 4K label on content streamed from the Netflix app and some others. However, the same content, when available in Apple's TV app from the same service, is correctly labeled as 4K content. Disney+ is not as transparent about the resolution of the content as the other services, so it's not clear if this is happening there as well. Local streaming services like Plex and Infuse also don't seem to manifest the issue. Further complicating troubleshooting and identifying the problem is the fact that the Apple TV upscales content to match the resolution of the output device.
Apple TV 4K: It could be a bug in tvOS
So even if the TV says it is receiving 4K, that doesn't mean that what is being streamed from the streaming service to the set-top box is actually 4K. Interestingly, these problems do not occur for all users and are not reproducible. The original Apple TV 4K, on the other hand, does not have this problem. According to reports, the problem only appears on the new Apple TV 4K and is also recorded in the beta of tvOS 14.7. So theoretically it could be some kind of bug in tvOS that affects some users but not all. There is currently no official statement from Apple on the matter. Apple's online support reportedly allows users to replace HDMI cables and perform a software reset. But neither of these seems to solve the problem. (Image: Apple)