What is this nonsense? Every user choose to run whatever OS and version they want (even Windows 10 users can block ALL updates). Does it really matter how many use which OS or who is right about the numbers?
I know many who still run MS-DOS 6.22(and even older), Windows 3.11 and NT 3.51. So what? These computers have specific tasks and there would be absolutely no point in upgrading the OS. They simply just work without a glitch on very old or simple very cheap hardware.
Personally I currently run Windows 10 (Latest release Preview), Windows Server 2012 R2, brandless Linux built from source, Ubuntu, Android, DOS, MenuetOS and KolibriOS...and many more. I bet this usage is not logged anywhere in the stats.
EDIT: Oh, forgot to mention that I also run Amiga Workbench (multiple versions) too.