I can't think of any case, except if you are too lazy to pass a file descriptor to another process, and its easier to pass the name (which cannot be ruled out, it is easier!). You can't safely close and reopen the file, or it might have been modified.

There is still a possibility that an attacker opens the file before you unlink it and starts writing to it, which O_TMPFILE gets rid of as it never has a name so can never be opened.