Of course the inhabitants could not tell the difference. If they could, they would. They would, for instance, comment on the existence of discontinuities in their world, and publish scientific papers about them — that is, if they could survive in the shuffled spacetime at all. But from our magical vantage-point we can see that they do survive, and so do their scientific papers. We can read those papers, and see that they still contain only observations of the original spacetime. All records within the spacetime of physical events, including those in the memories and perceptions of conscious
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What Deutsch is saying is that while the external observer would see time out of order, the experience of the internal observer would be to see events as they happen continuously because that is how, in each snapshot of time, even out of order, they consciously observe their reality.
