I believe Cliff's day job is scientist (physicist) which is why he tries for objectivity and repeatability.

But his testing methods don't make that easy: at the end of the workweek he may grab half-a-dozen knives and hike into the woods for a few days, and knives are evaluated on how well they actually prepare the meals he eats, the shelters he sleeps in, the fires he starts, etc. So some subjectiveness and variability is inevitable but the testing itself is certainly far more relevant than bonehead testing.