Field notes should make a body of thought easier to browse.
Not every idea needs a long piece.
Not every reader wants a straight path.
A field note gives the thought a small handle.
Then the graph can show the relationships.
This makes the body of thought easier to skim, enter, revisit, and hand to an agent.
It also respects how thinking actually moves.
Sometimes the useful path is not chronological.
Sometimes it is conceptual.
The notes make that path easier to find.