Those are Directed Acyclic Graphs (DAGs), like used in make, and Snakemake. No mention of that word though. There are some nice libraries and visualization tools for DAGs.
That's a coincidence, that the author only picked recipes that are made without cycles. Other Factorio recipes (e.g. nuclear fuel processing) are cyclic.
I thought you could go between heavy and light oil cyclically, but I think the recipes I'm thinking of are from UltraCube. The others are a subset of nuclear (Kovarex and reprocessing), so I think you're right.