Per Microsoft Docs:

GetVersion may be altered or unavailable for releases after Windows 8.1. Instead, use the Version Helper functions. For Windows 10 apps, please see Targeting your applications for Windows.

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 or Windows 10 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.

In short, GetVersion is no longer a reliable or accurate method for obtainin the Windows OS version. This also applies to GetVersionEx (docs). Alternatives should be investigated, or its usage should be removed entirely.

The C driver currently invokes GetVersionEx in mongoc-handshake.c in _get_os_version, used to set the value of the "version" field in handshake messages:

{ "isMaster" : 1, "helloOk" : true, "os" : { "type" : "Windows", "name" : "Windows", "version" : "6.2 (9200)", "architecture" : "x86_64" }, ...}

The C driver also invokes GetVersion in TestSuite.c in TestSuite_PrintJsonSystemHeader, used to report the release version of the host environment's operating system in which the test suite is executed:

{
  "host": {
    "sysname": "Windows",
    "release": "6.2 (9200)",
    "machine": "8664",
    "memory": {
      "pagesize": 4096,
      "npages": 0
    }
  },
  ...
}