Part of the resolution issue is probably caused by Netflix silly requirements. You can use hardware that is perfectly capable of handling 4k@60 or even higher, in whatever codec they deliver. But if your hardware is not considered as supported, good bad. An argument can be made for ease of use and general consumer base, but these things shouldn’t punish everyone else for that.
I honestly don’t know. Could be they rated it that way.
Just wanted to point out that Netflix in general is pretty iffy about fulfilling their promises when it comes to 4k.