I just pointed out that you can have a unified programming interface without a unified GUI, and then you point out that windows 7 had a unified GUI.But Windows 7 supports the SAME input methods as and has a unified UI across desktops and tablets. Of course that's not worked well in tablets but Windows versions prior to 8 all but ignored touch beyond an input method. In a way Windows 8 simply balances out and pays more attention to things that were already there and have been before anyone knew what an iPad was.
What's your point?