So…you can transform it into a threaded interpreter?

This seems like a ton of LLM verbiage making two simple and very standard techniques sound artificially profound.

> If you build flattened a vector of them

Well, yes, it's an old way to represent ASTs: allocate them all sequentially from a huge arena (worked especially nicely for BCPL). Except the author actually uses their home-grown vecte<Element*> which, as far as I can tell, uses malloc/realloc. And there are several pointer indirections inside the liste/ITEM/LIST classes so... yeah.