I have not yet seen a storage system that is actually 100% S3 compatible. Either functionality is missing, and/or there are corner cases where the behavior is just slightly different. It is also a complicated API, that often looks like it is a reflection of some internal engineering choices that were made (e.g. the object metadata structure AWS uses probably is the reason why the list call you mentioned behaves the way it does on AWS S3)

However, in this case, MinIO makes the deliberate choice to deviate from AWS S3 behavior, on a very common call (listing objects). I do agree that this has the risk to break applications in non-obvious ways, e.g. the call succeeds, bu t your application behavior differs, compared to running against AWS S3, due to the missing directory entry.

I also find their argumentation in the ticket a bit worrisome, calling the AWS S3 behavior a "blunder". I saw the same hubris when looking at their data path, where they choose to ignore battle-tested approaches like Paxos / Raft for distributed coordination, and instead build their own distributed lock algorithm and implementation: it does not seem to persist state, so resilience to power failure and server/process crashes might not be what you expect.