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.
I think you might have misread the table. Windows 8 64 bit looks to have about a 1% lead on the four versions of Mac OS listed:
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%
No. According to the Steam hardware survey, for November 2012 Win8x64 has a 4.25% install base (less than WinVistax64). Win8x32 has .44%, so Win8 has a combined percentage of 4.69%. By comparison, the top four OSX versions have a combined percentage of 3.26%. WinXP has a combined percentage of 10.83%, and Linux isn't even a blip on their radar.
Misleading is putting it kind of nicely. It's flame bait. According to their data, only Win8 64bit is surpassing OS X, and even those are segmented in to releases. What's more, the main argument is that Gabe called Win8 a waste of time, but is supporting Mac, but the great majority of the userbase is still on Win7 (over 70%), whereas Win8 combined is under 5%. WinXP has larger share than Win8.