This is hardly casting doubt on the nature of (human) death. This is purely a question about quantum mechanics, I'd say.

On a side note, I fail to see how the experimenter is supposed to survive with probability 1 in Everett's many-worlds interpretation and thus be able to distinguish the latter from the Copenhagen interpretation. Yes, there will be one world where he survives but in the "vast majority" of worlds he will be dead. (Disregarding for a second that counting how often the world bifurcates in the many-worlds interpretation is a somewhat delicate issue.) So in terms of probabilities, he will still die with absolute certainty as the experiment gets repeated infinitely many times.