I hope this helps a bit, this is taken directly from First Field Guide to Frogs of Southern Africa by Vincent Carruthers. I was looking through an older book of mine called Bill Branch's Reptiles of Southern Africa and that was first published in 1991 and in there they still state that the Giant Bullfrog could have a subspecies which occurs in Natal and Mozambique. So I would think the new classification is relatively (>10 years old) new.