Such arguments are based on how one draws the hominin family tree, and the exact classification of "Australopithecus" species with each other is quite contentious. For example, if the South African "A. sediba" (which evolved from "A. africanus") is considered the ancestor or closely related to the ancestor of "Homo", then this could allow for "A. africanus" to be placed more closely related to "Homo" than to "Paranthropus". This would leave the Ethiopian "A. garhi" as the ancestor of "P. aethiopicus" instead of "A. africanus" (assuming "Paranthropus" is monophyletic, and that "P. aethiopicus" evolved at a time in East Africa when only "A. garhi" existed there).