For one thing, it doesn't make sense in reference to the timeline. There is over a month between Rand's epiphany and the meeting at Merrilor at the end of the book. I find it hard to believe Aviendha would take that long to think about what she saw and confer with the Wise Ones.

Aside from that, it would be ridiculous for them to introduce this mystery after it had already been resolved. Team Jordan might not be perfect, but I doubt they are this horrible when it comes to planning a book. It makes no sense.