Now, the above screenshot has emerged in China, claiming to be the genuine screenshot of separate volume controls on Windows Phone 8.1. This has been posted by WPBar and they have been really active with Lumia 1520V leaks. They mention that users can choose to turn on or turn off this feature, users can select into the right corner of the sound settings to turn on this feature.
We could just confirm from one of our sources that this screenshot is the real deal and the final version may have more controls.
Thanks Xio-Feng for the tip. Cheers!!