A GetVersion leírásánál meg ez áll:
With the release of Windows 8.1, the behavior of the GetVersion API has changed in the value it will return for the operating system version. The value returned by the GetVersion function now depends on how the application is manifested.
Applications not manifested for Windows 8.1 will return the Windows 8 OS version value (6.2). Once an application is manifested for a given operating system version, GetVersion will always return the version that the application is manifested for in future releases. To manifest your applications for Windows 8.1 please refer to Targeting your application for Windows 8.1.
Másszóval: Kedves programozó, ez a függvény visszaad valamilyen verziószámot, ami vagy valós információ, vagy nem. Inkább az utóbbi.