Reading "subjective" to mean "nonexistent" is a potentially big mistake.
Objectivity is more accurate, sure. The winner of an objective contest is always objectively better against objective criteria. But, objective criteria are generally narrow. This works well if one is either (a) seeking fundamental principles like in physics or (b) the narrow objective criteria is the definite goal.
In this area, we don't exactly know how to define narrow, objective goals & subsequent criteria. We can definee goalposts, but not goals. These are guesses at useful markers of success, useful to the larger goal of useful/novel ai.
Subjective goals have their own (massive problems), but since we can't objectively define the goals of ai research... we need to fall back on human subjectivity to define our subgoals.
IBM turned the model/paper into a toolkit: https://www.ibm.com/blogs/research/2019/08/ai-explainability... Their model seems to be a variant of decision trees that has a knob controlling how complicated the trees are.
And the evaluation was completely subjective, so there's not any meaning to the Duke people losing besides that the judges didn't like them.