Rather than designing to better fit the pixels you can see like on Windows, I'm pretty sure the Mac OS X hinting was designed to get progressively better as screen densities increased. Like their reliance on hardware acceleration in the window manager, it was a forward-looking technical decision built in to the OS.

Unfortunately, we got stuck in a 96 DPI rut throughout the 2000s and are only just coming out of it with high-DPI "Retina" displays. Now the Mac hinting decision makes more sense, and the ClearType technology looks bizarre, whereas for all the last decade it was the opposite.