I think precognitive dreams aren't extrapolated from the present. I think they're based on what happened in another world which had been in a state similar to the one ours is in presently. Actually I don't think that's what they are either, but I think that's closer to what's going on.

When people's precognitive dreams prove to be 'wrong', they generally assume that the extrapolation was mistaken, or that it was correct but 'things changed'. But in some cases it seems it wasn't wrong because things changed, that it was always wrong. And its not wrong as in being a bad guess, its wrong more like directly seeing something that's real, but which somehow isn't quite our future. I've only had one wrong precognition that I recall, but it clearly didn't fit the 'things changed' model, and I've seen this with other people's precognitions too.