I also changed to ″Novorossiya Governorate″. It is just overall linguistic logic: using ″Novorossiysk Governorate″ implies reference to the city of Novorossiysk, which is confusing for 2 reasons: first, there is now a big city in Russia of such name, secondly, the name of the Novorossiya Governorate implied reference to Novorossiya as is clear from the fact that the renaming of the province preceded the renaming of city, Ekaterinoslav.