There was a conversation on an email discussion list over the past couple days where one individual running WSUS to patch computer reported that Windows 8.1 was not shown correctly as a targeted system. Instead, it was being reported as version 6.2.
According to Microsoft, starting with Windows 7, the major version of Windows stopped changing and remained at '6.' So, henceforth Windows 7 was reported as version 6.1. Subsequently when Windows 8 was released it was reported as version 6.2.
So, if you're seeing this for your patching systems, this is the reason why.
P.S. Jason Sandys just floated me an additional note about those over email:
An additional quick note on this. Based on first-hand comments from Mark Russonovich, it’s more than just WSUS. It was app compat in general because they found many third-party applications simply checked for the major OS version and in the XP timeframe that meant they would simply check if the major OS version = 5 – this was by far the most common app compat issue with Vista because the major version changed to 6. Thus, by keeping the major OS version at 6, any less than intelligent third-party developers that insisted on checking if the major OS version equals 6 wouldn’t affect app compat.