This was listed as one of the bugs fixed in the update posted earlier this week. I'm not sure if it returns a 10 or 7.
This is all due to a change Microsoft made in Windows 8 to the API function to always return 6. They have a new version function that requires a manifest that states the program is compatible with the version. SO if the program is manifested compatible with Windows 8, it will always return 8 even if running on 10.
I have an example that uses a different function to get the version number so doesn't have that limitation.
http://www.topwizprogramming.com/freecode_osversion.html