The source to that information (as far as I can tell) is a Reddit post claiming to be from a Microsoft developer. I've worked with programmers dumb enough to write such a version check, so I totally believe this might be true, but I'd love an official source.
It's cute, because the dedication to backwards compatibility is so uniquely Microsoftian: "We're going to create this API that idiots will inevitably abuse or misuse. Then, in the next version, after all the idiots have abused or misused the API, we're going to deliberately return wrong results from it so that the idiots' applications don't all break." It's really baked into their DNA, all the way back to the early days of Windows where they replicated all those DOS bugs so buggy games that took advantage of them would still function on Windows.
Whether or not it's true, it's certainly not irrelevant. Application manifests only apply to applications. If an application aware of W10 loads a third-party plugin that isn't, the plugin will still get the real version.
This is a very real scenario when you consider the application is explorer.exe and the plugin is any software that installs custom context menu actions.
But the above isn't looking at (faked) version information / GetVersion, but the name of the operating system, which is not faked in any call that I know.
