This is misleading. Windows 8 has just passed 10.7.4. There are 3 more recent Mac Versions that have a higher install base than Windows 8. Hell even Windows XP has more Users than Windows 8.
Windows 8 64 bit 4.25% +2.40%
MacOS 10.8.2 64 bit 1.49% -0.11%
MacOS 10.6.8 64 bit 0.78% -0.20%
MacOS 10.7.5 64 bit 0.72% +0.03%
MacOS 10.7.4 64 bit 0.27% -0.27%
Edit: Formatting..adding all mac osx versions (1.49%, 0.78%, 0.72%, 0.27%) gives us 3.26%