Let's start this off step by step and slowly.

Decompression has two basic components: 1) physiological, and 2) the decay curve. The curve attempts to describe the on and of gassing vs. time and pressure, is very simple and basic, has a standard look that mimics most such curves where they apply to nature ( right down to the ratio of the distances that arms of galaxies are spiraled from each other ).

Very simply, the number two does not account for all diving is because of number one. Some divers get great results with anything that fits into the midrange of all the curve's parameters, i.e., not too deep, not too long, not too short, and a deco that would work theoretically many data points away from the profile being done . Then the hurt on a real deep short dive, or a long shallow one, or whatever. That is not the fault of the "model", it is the fault of the application in the absence of considering the physical.

Let's start with this and talk about it, and then move on.