This feels like a bug to me. Only privileged processes can change the ownership of a file. Calling chown makes no sense to me. I could understand trying to chgrp (and ignoring a failure) but not chown.
If you have some systems where it works and some where it does not then I would guess the ones where it works are choosing to use the non-atomic write function.
The non-atomic write is used on Windows, or if the sincedb_path points to something that is neither a character nor a block device. Frankly I cannot think of a circumstance where that would occur, but you seem to have hit it.