Even if it is bypassing the file system, S3 is itself essentially a file system. It has all the usual features of paths, permissions, and so on. I assume it can't completely escape the same issues.
S3 didn’t used to be strongly consistent, though surprisingly they delivered https://aws.amazon.com/about-aws/whats-new/2020/12/amazon-s3... which I hope they’re proud of.
Some people have been crazy enough to store tables of padded data in the keys of a lot of zero-length objects (which they do charge for) and use ListObjects for paginated prefix queries. It doesn’t much matter whether keys have slashes or commas or what.
Let's call it "Ring -1"