[zozbot234]

AIUI, one obvious difference between object storage and file system (beyond things like support for directories and file name lookups, which OP talks about already) is that an object storage has only atomic file store/replace, whereas a file system has to support arbitrary edits on both file content and directories/metadata.

[Aperocky]

Yes, so file system is a superset of object storage, making this even less of a competition. It's easy to implement object storage on FS vs. the other way around.