That's interesting, thank you for pointing it out.
There was a not dissimilar potential idea to do something like that in hydrus for Windows NTFS, which can apparently embed tag-metadata for files and somehow search by it in Explorer, but I ended up not putting any time into it. I love the idea of exporting hydrus metadata to a filesystem, but these things are almost always platform dependent, and cool stuff like system:inbox or sorting by namespace is usually a no-go.
Again, it is interesting to me to see how other people approach this same problem of managing large collections of things. It surprises me that Linux devs so often avoid guis, even in the modern day.