Yes, people usually consider "S3 is files, but not a filesystem [1], and complaining about the missing features comparing to filesystem. But nowadays, the line between them is becoming blurred. S3 express one zone explicitly called their bucket as "directory bucket", and try to support atomic rename (even only for single object for now) [2]. GCP also has the same move ([3]). Posix fs APIs have its own pros and cons, and we are also considering to extend our metadata engine to support that in the future if it is needed.
[1] https://news.ycombinator.com/item?id=39656657
[2] https://aws.amazon.com/about-aws/whats-new/2025/06/amazon-s3...
[3] https://cloud.google.com/blog/products/storage-data-transfer...