I'm guessing a part of the point is that nobody had noticed anything (and indeed still can't, at least in any way they could report back) until the arrangement was pointed out, which highlights that there are bits in the standard notion of personal identity that get a bit tricky once you try to get more robust than just going by intuition on them. How do you tell you die when a matrix lord disintegrates you and then puts together an identical copy? How do you tell you don't die when you go under general anesthesia for brain surgery and then wake up?