Also I mentioned that even if you actually have a logical proof of something, you cannot assign a probability of 1 to the conclusion, because you might have made a mistake in the argument. You are pointing out some ways that might have happened here. Even if it did not, no one can reasonably assign a probability of 1 to the claim that they did not make such a mistake, and hence to the conclusion.
Also I mentioned that even if you actually have a logical proof of something, you cannot assign a probability of 1 to the conclusion, because you might have made a mistake in the argument. You are pointing out some ways that might have happened here. Even if it did not, no one can reasonably assign a probability of 1 to the claim that they did not make such a mistake, and hence to the conclusion.