The material environment draws inspiration from real-world forces, such as gravity and friction. These forces are reflected in the way user input affects elements on screen and how elements react to each other.
Material has its quirks, without a doubt. But the latest Motion guide makes a clear and logical argument for how motion in software design should work. Next: we need some sort of library embedded in our design tools to communicate these principles in our own mocks; until then, at least we have something to point at*.
*Of course, those designers with more time to spare should be able to prototype most of these interactions without too much trouble. But that's a band-aid on a bigger problem with our design tools.