Because "iterative refinement" is sort of wrong. It's not a refinement and it's not iterative. It's an entirely different model to physical simulation which works entirely differently and the speed up is order of magnitude.

Building a statistical model to approximate a physical process isn't a new idea for sure.. there are literally dozens of them for weather.. the idea itself isn't really even iterative, it's the same idea... but it's all in the execution. If you built a model to predict stock prices tomorrow and it generated 1000% pa, it wouldn't be reasonable for me to call it iterative.