Since time passes differently in Tel'aran'rhiod, Birgitte did not know how long it had been since Gaidal had been spun out. She says so herself, and doesn't know when she will be spun out though we know it would still have been years until then.

We, who have knowledge of how much time has elapsed in the real world, know that he is not old enough to be Olver. And incidentally, in a conversation with Nynaeve it is established that the expulsion coincides with birth.