"Fair" Grading

Not a long essay today- just an interesting tidbit. Wits (the University of the Witwatersrand, where I'm teaching) has a policy that all courses must include final exams, which count for at least 50% of a student's grade- and that each batch of exams must be graded by the professor and then reviewed by an outside evaluator. The evaluator must be from the same discipline or field, but cannot be connected to the University. I'm interested to find out the precise history of this policy, but apparently, it was implemented as a response to complaints of unfairness in grading. This is so interesting to me, as I’m someone who believes that grades are totally subjective anyway. I’m sure it stems student complaints, if nothing else.