FYI:  To be fair to the IBM systems of the time, TSS and MTS had a naming scheme that used dots (.) as the path separators in their pathnames and they too supported a directory/subdirectory idea.   While ugly in my opinion compared to UNIX, not really much worse than later schemes that DEC would use for TOPS, RSX, VMS et al (I once got into a "discussion" with Cutler about VMS's #$%%^ filenames but that's a different story).

The key point is that around this time the idea of "sub-directories" began to become important.   The file cabinet metaphor was beginning to come into age as people recognized the systems using "soft files" had the same issues that "paper files" and they needed some way to build up similar "filing mechanisms" with cabinets, drawers, file folder etc....

That said, I agree that  OS/360 was primitive but being batch oriented, I think did not consider the "human factors" the way the time sharing system required started to do. 

Anyway back to Warren's questions -- the idea of a disk "catalog" for the meta-data was not new to UNIX.   Tannenbaum's books (starting with the Minux book) describes the history and the idea reasonably well.    What UNIX did was create a user file type called  a directory (eventually user create-able) and was able to separated the human name for the bag of bit (i.e. the data itself) from the catalog or system name for those same bits.   As AST puts it, UNIX has a two level file system, one for the OS which is numerical in nature (the i-node) and then layered on top of it was something humans liked better.

Again, by breaking the idea/metaphor of a files and file cabinets into two pieces - higher level (human oriented) and lower level (system specific), like the splitting the command system of the shell out of the OS fork/exec/wait primitives, UNIX ended up with something more more flexible and scalable.

Clem