Apple only allows streaming, not downloading, of upgraded 4K movies

However, some HD files will still include HDR and Dolby Vision. Apple says, “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.” And if your Internet speed isn’t fast enough, the quality of video will be downgraded to what your connection can support. – Swapna Krishna, Engadget