Also what size your file manager should be is a function of what else you have on the screen which is inevitably variable so you end up resizing and moving windows to fit in with an arrangement that is different than last time you opened that directory. It's vastly easier if you want 2 directories shown side by side is to just use the traditional split view.
The fact that size and position are arbitrarily chosen even if they are per directory means that there is no mental map between position and position in the filesystem hierarchy.
Spatial browsing is a poor metaphor based on nothing that never made any sense whatsoever.
Relatedly, IMO iOS took a huge step backwards in UX when iOS7 moved away from a highly spatial interaction metaphor for practically the entire OS—by which I don't mean the skeuomorphism, exactly, but things like folders sliding the screen "open" when tapped, so that they had a sense of physical location within the main screen. Or "slide to unlock" looking like a physical slider so you didn't even need to read it to know what to do. The loss of the security blanket that was the physical (or at least faux-physical) home button has hurt it, too.
It also only worked well when you only had a few files in any folder. If you have 100 files that are related in one folder and you can't find anything without sorting it alphabetically. Depending on how your brain organizes things this might not matter.
> Where's file X for project A?
> On the floppy disk for project A.
And that more or less continued for most users through the 90s, but then it got confusing to the entry-level user:
> Where's file X for project A?
> In My Documents, under the folder "Project X".
Which, I'd bet, is one of the reasons why cloud-based editors have taken off - the file is "in Google Docs", rather than in a directory hierarchy on the filesystem. GDocs presents me with a more or less flat view of all of my documents. I hate this - I have to go over to Google Drive to organize them - but I can understand how it'd be much more approachable to the average user.
It's basically hidden entirely in iOS, probably for this reason.