When we come to the Joseph story, the famous Egyptologist, Donald Redford, argued that the entire episode should be treated as a seventh century BC literary construct. Yet this seems a step too far, and one that is not required by the evidence.
Nevertheless, not everything that is found in Genesis is historically accurate. For example, the J Source narrative about Joseph includes a reference to camels as beasts of burden, which is likely to be anachronistic.
Also while it is likely that the E Source writer has expanded on the original Akkadian material for his Joseph story, objective criteria for identifying any such elaborations are not easily established.
Yet in most cases we are entitled to view the E version of the Joseph story as one seen through the eyes of one of Joseph’s grandchildren, possibly Machir, who alone is mentioned at the end of this account.
A wider look at the evidence for Joseph as a historical figure is found here.
Bibliography
Donald Redford, Egypt, Canaan and Israel in Ancient Times, (Princeton University Press, 1992).