This is not a bug. It is a very intentional feature, like the scroll bars, they decide they had to go against the norm to implement it and they went aead with i

This is not a bug. It is a very intentional feature, like the scroll bars, they decide they had to go against the norm to implement it and they went aead with it. The intended use case is to allow the app access to both the screens. Imagine this in say a video editing environment where you could have the video playing on the left and all the myriad number of controls on the right. The problem is, to my knowledge, almost no app has taken to it yet, no one wants to be the first, heck not even apples own apps feel the need to do it. Conjecture-> The problem is unlike scroll bars you can't have a setting to disable it, because that would mean the app had to retroactively allow itself to run in a single window full screen mode which might be considered unpredictable behavior, something they don't like. So to give them some benefit of doubt I see where they're coming from.