High order means much less dependence on step size. Automatic (exact) differentiation means no roundoff from finite differences with small step size. They use a very clever and involved code generation approach, I have just hardcoded the recurrences in my implementation (much simpler). https://github.com/m4r35n357/ODE-Playground

It is not a black box approach like RK4, it depends on the model using a (hardly at all) restricted set of functions. Piecewise definitions are OK though.