Microsoft forever does battle with well-intended code that a programmer writes to check the Windows version. Which was typically written to deal with older Windows versions. But forgets to do something reasonable with a newer Windows version.
So they spend massive amounts of effort on targeted compatibility shims that intentionally lie about the Windows version when a specific program asks for it. A never-ending battle whenever they release a new Windows version. Certainly a losing battle, the number of programs they need to test is staggering.
So at Windows 8.1 they said "no more", deprecated GetVersionEx() and intentionally lie out of the box, returning version 8.0. You need to add an entry to the manifest to turn off the lie. Which probably will turn off a lie about the service pack as well. Or might require an updated GUID, fairly unlikely. We of course can't be sure until that happens.