If someone else applied a non-removable custom theme to your Windows7 install it is certainly no longer "true" Windows7. The power relationship matters.
So at that point apps that worked in my "true" Windows7 would no longer work in this new non-removable custom theme version of Windows7? Because that's my threshold of whether it would be Windows or not.
It's like Asus releasing laptops with Windows 7 and AsusFlash. AsusFlash would replace Explorer.exe as the shell, leaving you with some other weird interface - left clicking opens menus and you have to drag icons to a bar along the top to open the program.
Now, SP1 comes out, but Asus hasn't released SP1 with AsusFlash, and regular SP1 gives you the error "Please install your OEM Vendor specific SP1 patch". And you don't have the BIOS password either.
Later, SP2 comes out but no "AsusFlash SP2" and you're still on "SP0", the unpatched Win7. Are you using "True Windows" anymore?
Yes, it just can't be upgraded to the latest version. If it can still run Windows applications it is Windows regardless of how badly an OEM ruins the install.