I suppose it is convenient to handle the documentation in that fashion, but it sure feels like a fork in the language. One language set when working with Apple OS, and another set when elsewhere.
Combine, and admire the incredible, herculean work that those teams presently are engaged in. But, I am concerned about the implications of their decisions on the future development of the language.
For instance, one could imagine a future in which there would exist a
UserInterface framework, with that framework providing (i) types to specify universal UI elements, and (ii) a set of protocols to provide an interface between those universal types and any given OS, with the platform provider (or the Swift-on-Linux project) to write types that conform to the interface protocols.
SwiftUI may be a big step down that road; or it may, through inertia and/or due to naming collisions and/or for other reasons, become an impediment to growth in that sort of direction or other directions. I'd appreciate the thoughts of the community on that topic, but perhaps that discussion should be saved for some other thread.