macOS fakes fractional scaling by rendering a larger image at 2x and then downscaling it. For example, 1800x1169 renders a 3600x2338 at 2x scaling, then resizes the rendered image to 3024x1964. This is slower and looks worse than true fractional scaling would be, but makes the implementation a lot easier and in practice it’s hard to tell the difference. It’d look pretty awful if the native ppi wasn’t so high.