i think they are probably laying the foundations for the Blood Raven origins with the tale in Age of Darkness.
i know theres not much hard facts but it has more to it than some of the theories for many things
40k that are going around.
EDIT: lexicanum also states "
Possessed of powerful Librarians, the Blood Ravens are noted for their ability to predict enemy movements " which was the particular aspect of the Thousand sons that the Corvidae excelled at. they also wore a Raven as their symbol as being a member of the Corvidae.