Aside from resolution of paths to some canonical version (e.g. collapsing redundant /'s in your example), what actually is an "actual directory" other than a prefix?
An actual directory A with 2 child directories A/B and A/C, each of which with 1 million files, doesn't need to go through millions of entries in an index to figure out the names of B and C.
It's also not possible for A and A/ to exist independently, and for A to be a PDF, A/ an MP4 and A/B a JPG under the A/ ”directory". All of which are possible, simultaneously, with S3.
An actual directory is a node in a tree. It may be the child of a parent and it may have siblings - its children may in turn be parents with children of their own.
