Content 4K on iTunes are limited only to streaming, not to download
The iTunes Store is already available content in 4K for the new Apple TV, but this news is limited only to the stream and not the video downloaded by users.
As confirmed by Apple, the movies in 4K are not available for download and cannot be watched without an internet connection. In practice, on the iTunes Store the only content in 4K are the ones streaming: Apple explains that customers can download in a local copy of a HD movie (sometimes with support HDR and Dolby Vision), but the film 4K are not available for download and can only be transmitted in streaming. There is therefore no possibility of being able to download locally.
Also the new content as soon as you have purchased and downloaded will only be available in HD, perhaps for the issues of licenses. It is not excluded that this limitation has been enabled by Apple to avoid problems of local storage, since the movies 4K take up a lot of space.
Also, for streaming content in 4K on the new Apple TV, the company recommends a minimum speed of connection is the same 25MB/s. If the internet connection is not fast enough, Apple will reduce the video quality.
Apple also confirms if the 4K video on YouTube can only be played in HD, since watchOS does not support the format Vp9 of Google its own this type of content. Vp9 is a codec that is not supported by Apple TV, which instead supports the H. 264, ready hevc (H. 265) and MP4. No problem, instead, to content 4K Netflix.
Link to the original article: the contents of The 4K on iTunes are limited only to streaming, not to download