WOW, you’re right! I just checked my iTunes copy, and it looks REALLY good! It’s still only HD for me (hopefully it upgrades to 4K for me eventually – iTunes usually does!), but it’s definitely the new master. It looks WAY better than the old green extended Blu-ray master!
So I’m curious about something. When you stream the new master from iTunes/Apple TV on an 1080p SDR monitor, what are you actually watching? I get that the 4K would just be downscaled to 1080p, but what about the HDR? Is there some kind of tone mapping being done, or does Apple already have a 1080p SDR version of the new master that automatically streams if they detect you’re using a non-HDR screen?