It’s due to the Retina displays. The scaled resolutions don’t map in a clean way to pixels. The renderer renders everything at the native resolution of the pane

It’s due to the Retina displays. The scaled resolutions don’t map in a clean way to pixels. The renderer renders everything at the native resolution of the panel and then has to downscale it to the scaled resolutions. For the “native” Retina view, it’s just /2, so it’s easy and pixel perfect. The others are more like /1.523134... and there’s more work to figure out what color each pixel should be.