I agree that it would have made sense for someone to question Birgitte about the Age of Ledends but she may not have been the treasure trove of info. Yes she would have known about the various types of shadowspawn like the Gholum etc but Birgitte had made it very clear that in nearly every life she was a solider not a scientist or leader. She was really uncomfortable being Elaines Captian General of the Andoran Guard even though she is quite compitent.

If you think of it this way if the average US/European solider was frozen mid way through a terrible world war and woke up in a world that had reverted to 17century level technology could that solider tell the powers that be how to get computers going, how to build jet fighters how to build a power station? Not unless that soldier was an engineer.

Say that soldier was pretty skilled and say part of an elite unit like the Delta Force or the SAS would that soldier know the ins and outs of the battle tactics of the enemy. He/she might have some insight but they would only have seen a part of the battle they would have been invovled in planning individual missions but not the overall running of the war.

Birgitte could give some insight to the forsaken and some of their tactics and habits. I doubt if she could go too much into how the sealing went as A) I could be wrong but was she dead at the time and b)she was not an Aes Sedai and it was a pretty technical project.

She might recognise some Ter'angreal but again she was not Aes Sedai and they came in all shapes and sizes. Her best source of info was proably about the rarer types of shadowspawn that were common in the war but are less often used now and are being kept in reserve eg. the Gholum.