Well to be technically I am not sure the Prophets can get things wrong so them being right is no surprise although like all oracles they are scarce on the details.
Right. The so-called Prophets aren't just having visions of the future, they exist
in the future. They have firsthand experience of what it holds. Any inaccuracies would have to be matters of interpretation, either the Prophets' interpretation of what they witness firsthand or the listener's interpretation of how they describe it.
Although that doesn't address the question of branching timelines...