An update for Windows Server Update Services 3.0 Service Pack 2 is available (KB2734608)
Additional note on KB2734608 regarding WSUS, Windows 8 and Windows Server 2012 (Link)
Even after all that, still not showing patches, but also still reporting at Windows 6.3.
Here is how to change the Windows 6.3
Log on to the WSUS server and open notepad. Paste in the following text:
UPDATE SUSDB.dbo.tbComputerTargetDetail SET OSDescription = 'Windows 8.1 Pro' WHERE OSMajorVersion = 6 AND OSMinorVersion = 3 AND OSBuildNumber = 9600
Do file save as Add-W81-to-WSUS.sql and save it to C:\temp
Now run this in an elevated windows command prompt:
sqlcmd -I -i"C:\temp\Add-W81-to-WSUS.sql" -S \\.\pipe\MSSQL$MICROSOFT##SSEE\sql\query
It will say X number of rows affected. The X should match how many Windows 6.3 machines are showing up in WSUS.
Now just as aheads up... if you aren't getting any Windows 8/8.1 patches double check that you are synchronizing them haha!
UPDATE: I just noticed that it reverted back. Will look more in to this. From past experience you might have to commit the update.