It looks like Apple is changing the labels based on the device you view the movie info on. For example, I own Alien Covenant, Logan, Spiderman: Homecoming, Wonder Woman, and other movies that originally showed as 4K HDR on my 2017 MacBook Pro, but no longer do. But if I view them on my iPhone X, they show as 4K HDR.
Perhaps they at some point determined the MacBook couldn't provide a proper 4K HDR experience and removed it. Probably the MacBook does not have the necessary contrast, as its max brightness is ~500 nits, compared to the iPhone X's ~625 nits. Also the iPhone X has OLED for zero blacks whereas the MacBook is backlight and cannot achieve the same. Neither has true 4K resolution.
It's confusing though, because the iTunes store has sections for "4K HDR" but then if you go in there and view the movies on a non-HDR device, they don't show 4K HDR. So this makes it difficult to shop for these 4K HDR movies on your main computer or iPad (generally easier than using an iPhone or Apple TV).