No, it's not. This is a bug. macOS has two rendering modes: Normal (1x) and HiDPI / Retina (2x). For this reason, most apps have two different sets of assets l

No, it's not. This is a bug. macOS has two rendering modes: Normal (1x) and HiDPI / Retina (2x). For this reason, most apps have two different sets of assets like icons and other images shown in the UI. After rendering the content either at 1x or 2x, the picture is scaled to the "real" resolution of the display. This allows Apple to support a large number of "scaled" resolutions, but the apps only have to support two modes (1x or 2x). You can see that this happens if you have two displays attached to your Mac, one with Retina and one without. When you drag a window from the Non-Retina-Display to the Retina-Display it will be pixelated at first (it was drawin in 1x mode), until it's completely on the new display, then it will redraw in 2x mode and become sharp. Normally 1x mode is faster. Try opening an app that shows a lot of data (eg. a large spreadsheet) and scroll quickly on a 1080p display vs. on a 4K display. You'll should see that the scrolling is much smoother on 1x than on 2x, since the 2x display needs to draw four times as many pixels. So this is clearly a bug, and not because of some additional scaling from 2x->1x. As this blog post shows, it's faster when downscaling from 2x.