It may look “random” from the point of view of the applicant – but it is a subjective,holistic process and the ad coms know what their priorities are and they are making very deliberate, considered decisions. The problem with your statement is that the colleges do not use test scores as a sole determiner, or even a primary criteria. The test scores aren’t considered in isolation-- they are considered in context of other factors, like GPA & academic record – and that information is used as a first round screen.
It’s quite possible that my kid would have been an automatic reject if her GPA had been 3.2 – but it wasn’t. She had a high GPA that counterbalanced her test scores. It’s typical for schools to compute some sort of academic index, but they each have their own formulas. But the point is, they would never be looking at SAT scores in isolation.