Re:Hold shift and hit the minimize button on OS X
by spilk on Thursday August 07, 2014 @12:35AM
(#8146295)
Steve demoed it during one of the Macworld keynotes, so I don't think it's too much of a stretch to think it was put there so he could demo the effect. I recall him minimizing a playing Quicktime window to show that the compositing window manager was drawing the video in the 'genied' window.
This is why it exists.