One possibility is that our intuitive sense of 'is this statement likely to be true' is developed to detect lies by other human beings, rather than to simulate the external world.

For example if someone is trying to convince you of a tribe members bad behaviour, the ability to produce extra details (time/location/etc) makes it more plausible they are truthful rather than lying. However in probability terms each extra detail makes it less likely (e.g. 'probability of bad behaviour' * 'probability of doing it in location x* etc).

[Cross-posted in the original thread]