In context of the comment I was addressing, it’s clear that filesystem means more than just a key value store. I’d argue that this is generally true in common vernacular.
This is a technical website discussing the nuances of filesystems. Common vernacular is how you choose to define it but even the Wikipedia definition says that directories and hierarchy are just one property of some filesystems. That they became the dominant model on local machines doesn’t take away from the more general definition that can describe distributed filesystems.
I'm kind of chuckling at this thread because you're working so hard to not understand.
I think the previous poster could/should have said, "It is not a hierarchical file system and has no concept of directories." where I added the word "hierarchical".
I disagree with that characterization because the contrast by OP was that S3 is “just a KV store implying” it doesn’t meet the criteria for being considered a filesystem.
For example, you could implement POSIX directory semantics on top of S3. About the only POSIX filesystem API you couldn’t implement it append / overwrite (well you could but it might be prohibitively expensive).