I think it's definitely a clear definition of what you're doing, but I still take some issue with the framing of "UI pixels". I would argue that it's more like abstract "UI distance units."

Most UI's are designed to be "right-sized" for humans with a "distance unit" being about 1/96th of an inch (when the display is the designer-expected distance from the user). If you deviate too far from this, things end up being really big or really small and the display is harder to use. What you're effectively doing when you enable "2x scaling" is setting the "abstract distance unit" that gets applied to UIs to be the size of two display pixels, rather than one display pixel. Whether this is a good thing to do and is more or less "native", IMO, depends on the DPI of the display.