It might be a Canadian thing, then. Cheap Charts has it listed as 4K in the Canadian store, but not the American one. I'm sure it will be coming soon. They're usually in sync.
A bunch of my 4K Warner titles dropped down to HD yesterday - 2001, The Shining, Superman The Movie, The Shawshank Redemption and a few others. They even show up as HD on the landing page. I assume it's just some kind of temporary glitch, as a number of other Warner titles are still coming up as 4K.
I had a look at a few scenes last night and it's...not great. It looks sharp enough, but it's been completely degrained. It looks like digital video, which I can't imagine is something Tarantino would approve of.
The three blu-rays all look completely different. And the Shout Factory and Arrow (and presumably the 4K) were approved by cinematogrpaher Dean Cundey.
I had this in my iTunes library, so I had a peek at it last night. I didn't watch the whole Thing, but did skip through select scenes. I already have the three previous blu-rays of this, and the 4K looks closest to the first disc, in terms of colour, though obviously without the DNR. It's also...