That's it. And the linearizer is only one way-- you write text with [[links]] and turn that into plaintext.
Previously I'd thought of using transclusions for things like long-lived documentation. Now reading about Leo it seems like they'd be just as useful for creating short-term views into one's code. Eg start a refactor PR by transcluding all the relevant definitions into a doc. Now you can start writing PR comments in that doc before you even begin coding, and when you do all the relevant code is right there.