Yeah exactly. The immersive mode does not lock the app, as you can swipe from top to bottom to get to the notification bar.
I've linked to a youtube url in the OP, here is the full link: http://www.youtube.com/watch?v=BH0HXP-Z4z4
This will make it clear
It would be great if @bleu8888 could shed some light on this.
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