A few years ago, I actually searched around for an implementation of the classic finder, so this is very amusing for me to see actually implemented!
What I was interested in back then was the idea that there was a direct correspondence between the folder window and the data structure on the hard disk, and that to the user these concepts should be indistinguishable. One part of the illusion is that a folder always appears in the same place with the same window size, to give the sense that the folder is a tangible thing with permanence.
It's got a loooonnggg way to go (I never realized how many small but vital details are in a file explorer application), but it's strangely exciting to see it draw itself on modern macOS, especially on a retina screen!
And yes, the spatial UX! I'm still working through getting all of that implemented (I just completed persisting window locations/positioning days ago). I have recently been reading theough some of John Siracusa's turn of the Mac OS X era writings and that's been hugely insightful and helpful. The level of detail (both of the original Finder and his writings) is impressive and sirprising.
I also used to love the fact that the equivalent of kernel extensions (totally forgotten the name) could be disabled by moving them to a different folder. The file system IS the computer.
What I was interested in back then was the idea that there was a direct correspondence between the folder window and the data structure on the hard disk, and that to the user these concepts should be indistinguishable. One part of the illusion is that a folder always appears in the same place with the same window size, to give the sense that the folder is a tangible thing with permanence.