The story details of how Bruce Wayne bounces from time-to-time has yet to be revealed. The quote you pulled from the interview is Morrison speaking about Batman figuratively, not literally, as a character who needs to be reinvigorated to always remain relevant.
In other words Batman is literally an immortal god that can never age or die.
Last I checked the story details are that if Batman dies, he just gets reincarnated in a new fresh born baby body that looks just like a younger version of his original body with all his memories intact. He starts from the prehistoric times and continues reincarnating all the way to the present.
What more evidence do you need?