inspired by, but definitely not take from as not in evidence

Many people have "daily notes" and "project notes" in what they consider to be their zettelkasten workflow. These can be thought of as subcategories of reference notes (aka literature notes, bibliographic notes). The references in these cases are simply different sorts of material than one would traditionally include in this category. Instead of indexing the ideas within a book or journal article, you're indexing what happened to you on a particular day (daily notes) or indexing ideas or progress on a particular project (project notes). Because they're different enough in type and form, you might keep them in their own "departments" (aka folders) within your system just the same way that with enough material one might break out their reference notes to separate books from newspapers, journal articles, or lectures.

In general form and function they're all broadly serving the same functionality and acting as a ratchet and pawl on the information that is being collected. They capture context; they serve as reminder. The fact that some may be used less or referred to less frequently doesn't make them necessarily less important