Originally Posted by giga
Are you playing on an ATV 4K?
I'm seeing the same thing. Lego Batman - which I got from Amazon - shows 4K/Dolby Vision in my library but when I play it the pull down menu shows it's playing in HD/Dolby Vision.
Baby Driver and Spiderman Homecoming, which I got from codes redeemed on the Bluray via the MoviesAnywhere site, show the same behavior.
Hopefully it's just a quirk being ironed out.
To be fair, there's a bit a lot of growing pains in my experience (and reading other people's experiences online) with the HD->4K upgrades on iTunes. Movies showing 4K then changing back to HD then changing back to 4K, things like that.