The “Table of Contents” in the article (https://mainmatter.com/c-to-rust-migration-book/) looks like the very basic stuff and not especially interesting, but then the headings in the book itself (https://mainmatter.com/c-to-rust-migration-book/course/) look much more in-depth and don't seem to map onto the supposed ToC. I think they're misusing that term? I guess it's aspirational too as the book isn't finished yet.