Anyway, I used grep too, but I also navigate by following the links in my notes, which can sometime take me to different location. That can be a single file too or multiple files. That doesn't matter. What matters more is organization(or rather lack of).

With Zettlekasten, you build a concept map of topics that you wouldn't otherwise get if you write your notes linearly or chronologically.

So yeah, zettlekasten doesn't make sense as a productivity system, but that isn't its intended use case anyway.