Your second point is kind of confused. You don't need the prediction to coincide with the event, to judge the quality of the prediction. If I predict the elections for 2 years time then you can still judge whether I got it right or wrong. If I do that for multiple elections for multiple cycles, you can decide whether I'm a good forecaster.

If I then make another prediction that's always 1 year out, you can decide how good that prediction is and start to make a curve of how good my predictions are by how far out they are.

Taleb is saying that the blue line is so incorrect it's meaningless and deceptive and Nate should product a red line which is a real probability that he can actually be judged on.