Saggital Crest : so what ?
This very attribute has been reported even in sapiens. The most famous was Attila, the king of the Huns. The Huns, and other peoples, used to compress the skull of their chiefs' children, just after the birth, in order to obtain a pointed shape.
A significant point : there is no correlation between the degree of deformation and the ratio of sapiens/erectus features in the Kow Swamp/Coobool population, according to Milford H. Wolpoff, Department of Anthropology, University of Michigan, Ann Harbor (in Fossil Man - New Facts, new ideas, Anthropos (Brno), Vol 23, 1986).
There is also a great variability in gorillas for that matter (the first one is short of a jaw) :
My conclusion : these differences are not specifical ones, but most likely the result of different treatments of the skull just after birth, either intentionally or not.
A comparison of Patty and H erectus from Dmitri Bayanov's America's Bigfoot :
Gigantopithecus has never been found in America. Erectus has been discovered in America, at least at Santa Barbara.