In the Wheel of Time series, the Seanchan are great believers in omens. Our Andoran friends believe it is all superstitious nonsense, quite similar to how the Seanchan view tales of trollocs and other shadowspawn.
Were the omens know before Artur Hawkwing's sons set sail across the Aryth Ocean, then simply forgotten? Or was it something they discovered while they lived on their separate continent? I've scanned through the books and supplemental material I have on hand, but I haven't found anything obvious to indicate either way.