?? So the Samsung is fine because you can apply a theme to remove their skin, whilst Sony is in the 'wrong' for applying their own skin?! Are you serious?
Sony is by no means perfect but what you are saying makes little sense. What is clear is that stock android is great, the further away you get from this = not good. Sony is the closest to stock of the non stock manufacturers, which is partly why I prefer Sony over others (at the moment).
Don't get emotional.
Samsung kept the multitasking UI 95% stock - just added a bar to the bottom with 3 buttons. It looks and functions just like aosp. They're notification bar has has asop battery and signal icons - do sony? No.
Sony have skinned nearly every area of Android!
Point is when you add a custom theme to Samsungs TW it will looks like AOSP. And it's easily done - get the point?
There is no custom theme for Sony's UI that can change the multitasking UI.