I rented Baby Driver in UHD tonight, and I swore it was 1080p. I was talking to Google Support, and they swore it was 4k. I know what 4k looks like, dangit lol. They told me to go to youtube and look under my purchases, and there I could verify that it was streaming in 4k. Sure enough, the highest available resolution was 1080p.
its fake 4k anyways.
http://realorfake4k.com/my-product/baby-driver/
All services should take a play from apple, for once, and make all the movie qualities the same price