World Eater Librarians

In "Betrayer", we learn that the World Eater Librarians were made extinct though two methods.  Firstly, those that accepted the Butcher's Nails went insane and their powers became uncontrollable.  They were forced to volunteer for removal of the Nails, but that resulted in their deaths.  Secondly, those that (for whatever reason) did not accept the nails died of ... natural attrition and their colleagues...

Yet, it was not always the case.  Going back to Realms of Chaos (Slaves to Darkness), a different history is recorded.  Specifically that the World Eater Librarians were forced to give up their psychic powers in the service of Khorne.  Although they did have powers, they renounced them and became tally masters for the number of skulls taken and deeds done in the name of the blood god.

I'm not quite sure which I prefer.  I guess I like both of the alternatives at some level!  The newer version feels a lots more fleshed out (naturally) even if it is a ret-con to an old timer like me.