Sören Laue, creator and first author of this work [1] gave a nice talk [2,3] about it at our reading group not long ago. He also has written about how automatic and symbolic differentiation are essentially equivalent. [4]
[1]: https://papers.nips.cc/paper/2018/file/0a1bf96b7165e962e90cb...
[2]: https://www.youtube.com/watch?v=IbTRRlPZwgc
[3]: https://compcalc.github.io/public/laue/tensor_derivatives.pd...