Rename doesn't always do what we want. The one serious investigation I've seen [1] unhelpfully states that "[W]hen a file is appended, and then renamed ... many file systems recognize it and allocate blocks immediately." Suggesting that some file systems don't, but failing to name them. In general, appends followed by directory operations are not order-preserved.
[1] https://www.usenix.org/system/files/conference/osdi14/osdi14...