I’m pretty sure Seldon being wrong about the smaller things is going to be a recurring thing in the series. People just _think_ he can predict them. He seems to too, despite knowing rationally that he cannot (he’s stated that numerous times).
The theme of the Seldon plot seems to be: is Seldon predicting things, or causing them? Are his actions choices that are driving events, is he being forced into his role by fate (or math), or is everything he does irrelevant? Is the very fact that he, and we, are confused about this proof that the questions don’t even make sense? Can some of all these contradicting things be true at the same time?
Might it be true that he is _both_ predicting events and driving them? Wouldn’t that mean that one of these ideas is false?