Stumble upon this article about how Microsoft defines 4K.
What is True 4k Resolution? Is it Native resolution?
Interestingly enough on Xboxwire.com which is basically official Xbox blog, they actually made a post with a frequently asked questions and one of the question was about the true 4k resolution.
So in that page it was actually explained that true 4k resolution may consist of native 4k resolution checkerboard / sparse rendering resolution or dynamic resolution scaling. Which is interesting statement because it means that they are pretty much doing the same thing as Sony does with the dynamic 4k.
So, it’s going to be basically a war between dynamic 4k and true 4k resolution. Interestingly enough none of these companies is actually saying anything about native resolution because they cannot really promise a native resolution in every single game and that’s both for PS4 Pro and Xbox One X.
After reading that last line, I came to realize that I keep hearing true 4k as opposed to native 4K. That's because the phrase 'True 4K' is the same thing as other buzz phrases like "MotionRate 120" or "TruColor HDR" on TV's.
These phrases let companies say they provide something that's sounds similar to a certain feature without it being the exact same thing. Tv's with TruColor HDR try their hardest to mimic what HDR looks like on a TV that's capable of displaying more colors.
MotionRate 120 is a way to mimic 120hz using a 60hz panel.
The same with MS. They're pushing True 4K and calling their console a True 4K console. But what that really means is that they're delivering a system that puts out 4K like quality along with some actual 4K games. This gets them to say they have a 4K machine without having some or any actual 4K games. It also lets them avoid legal trouble.
MS' marketing is as sharp as ever!