I have both side by side and i think this is more of a myth. They simply render the same on hidipi except very small sizes where the engines differ.
On Linux font selection is terrible, people have problems with Wayland/x11 rendering and other settings (often opinionated defaults from distros).
But when you are lucky :)) you can get pretty much same hidpi font rendering.
Freetype at least has knobs that are both configurable and understandable. On Windows, you only have Cleartype Tuner, and it can be hard to get what you want.
I used to prefer font rendering on Gnome to that of MacOS and Windows, but as of Gnome 46, they changed it so that if you set a fractional scale factor, everything gets blurry (a different kind of blurry than the OP means) just like it does on MacOS, making Windows font rendering the desktop font rendering I like the best as long as I stick to relatively modern apps like browsers, VSCode and the newer apps that comes with Windows like Settings. (Legacy apps on Windows are super super blurry at fractional scale factors.)
I use non-HiDPI 1920-pixel-wide displays at scale factors between 1.25 and 2.0. (Yes, I like big type and big UI elements: my eyesight is bad.)
No, Linux (Gnome/Wayland) uses a method similar to macOS where everything is rendered at a higher resolution and then scaled down. If you have a very high DPI display it looks nice, but if the DPI is not that high to begin with you will notice that the result is a bit blurry. Only Windows has truly good scaling.
I agree. The blurriness at fractional scaling factors on Mac and in very recent versions of Gnome is obvious on a non-HiDPI display (at least a 24-inch one like the ones I use).
Until a year ago, Gnome/Wayland did it the way Windows does it! I.e. the method the OS used to make the text and the other UI elements the size the user specified refrained from applying any blurriness-causing resolution-scaling algorithm as long as you avoided the XWayland compatibility layer (and the compatibility layer that lets modern Windows support legacy apps makes the legacy app blurry, too).
Chrome's "zoom" feature (activated by the keyboard shortcuts Ctrl+plus and Ctrl+minus for example) does fractional scaling (i.e., allows the user to adjust the size of the text and the other UI elements) without introducing any blurriness. Installing Chrome and experimenting with that feature is probably the easiest way for the average reader to see what we are talking about.
One parenthetical detail is that (unlike on Mac or Windows) in order to get fractional scaling at all on Gnome/Wayland you have had to use a command line to add a particular key to a list named 'experimental-features', but that will change next month when Gnome version 47 will be released, at which time the user will be able to change the scaling factor in the Settings app just like one can on Mac or Windows without first having to configure anything or opt in to anything.
I would love to know the reasoning behind the Gnome team's decision here because just because although you or I might not be able to notice the blurriness on a HiDPI display or to say with confidence that the blurriness is there doesn't mean that the image is as sharp as it could be: the scaling algorithm used on Mac and on Gnome versions 46 and 47 is clearly throwing some "visual information" away regardless of the resolution of the display.