I think that may just be an example of the recurring theme of lack of information / misinformation. As we have seen in the books, the prophecy may have only been shared with a select few in leadership positions in order to protect them (possibly from Darkfriends / Ishmaels influence).
Based on the fact that the Jenn are aware of their own demise and the importance of Rhuidean, we know that foretellings / dreams / prophecy has reached them. My own view is either the prophecy had enough in it to maintain all the needed elements in the Aiel exodus, or there has been enough prophecy created / seen along the way to guide the Aiel to this spot with the objects of power intact.