There's 4K and then there is UHD 4K. While it riles me they messed with the terminology and today you are being asked to accept 4K to mean UHD 4K, as an engineer it's annoying.
https://en.wikipedia.org/wiki/4K_resolution notes what is DCI 4K and what is 4K UHD.
No TV I know of is 4K (DCI.) So where is the definition of 4K Ultra? You tell me.
I have recently bought an ultra 4k TV. I am looking for some apk to install and run which can validate if the TV is real 4k or not. Something like the antutu benchmarking.