I'm not sure if it's necessary either atm.Sorry but why? The Civics, as of SVN 9943, are working as designed in the Preh Era. At least they are on Epic GS and Immortal Handicap. I'm not sure where or what DH is looking at though. Just know from play last night and today on a new game that they are fine in the Preh Era and are costing 1 Anarchy turn in Ancient Era.
I've been talking to TB about adding a quantity discount on anarchy time. So the more civics you change at the same time the more turns is cut off from the resulting amount of anarchy turns.
In the process of adding that quantity discount there may be some calculation and logic changes. Changes that the era modifiers to anarchy time may need to be adjusted to.