To add, we don't know if the 4K model is true 3840x2160 or if this is another PenTile (RG/BW) display. Last year's Zenbook Pro UX501VW model used the latter.
I think in order to help avoid perpetuating the ability for ASUS and other companies to do this, we need to clearly and accurately call this out in articles such as these. A simple note such as "choice between '4K' (unconfirmed if true 4K or PenTile) or Full HD" I think would be a good start. More, such as "Last year's UX501VW, as well as a number of other ASUS laptops, used PenTile (RG/BW) displays for this spec, which stirred controversy because they do not produce the full detail of the resolution when compared to full RGB matrix displays, and because the difference tends not to be stated in product specifications. We do not know if this model has moved on from that." is of course always welcome.
To clarify, by "clearly and accurately", I mean to avoid using buzzwords that hold it to undue regard (don't call it PenTile "technology"), to avoid beating around the issue that PenTile is worse (don't compare it to the "traditional" RGB matrix, compare it to the "full" RGB matrix), and to avoid touting its "advantages" without putting them into context (a PenTile RG/BW display can use less power and cost less to make, but so can a "lower resolution" full RGB display with the same lower effective sharpness, which won't carry PenTile's issues or its tendency to be deceptively marketed).
There is also an unconfirmed rumor that the 4K model is cancelled, which is discussed in this thread: https://www.reddit.com/r/laptops/comments/7060hy/so_apparently_the_longawaited_ux550_4k_version/