A topic should lead somewhere besides the note you just read
When most topics contain one note, the labels describe the content without helping readers discover anything else.
You finish a note, click its topic, and land on a page containing only that same note. The label is accurate. The navigation has taken you in a circle.
This happens easily when every interesting word becomes a new topic. Each label sounds reasonable on its own; together they produce a growing menu of nearly empty destinations. The writer gets more precise descriptions, while the reader gets fewer useful connections.
A small, provisional vocabulary helps. Give a note one main topic and a second only when it adds another useful route. Before introducing a topic, look for several existing or clearly upcoming notes it could bring together. Three is a workable review threshold, not a law of publishing.
The vocabulary can change as the collection grows. A detail can remain in a title or paragraph without earning its own place in the navigation.