The manpage for
-prune True; if the file is a directory, do not descend into it. If -depth is given, false; no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together.
What is the meaning of the last sentence? Can't one usefully run the below command...
find /path/ -prune -type f -ctime +15 -delete
... to find and delete all files last changed more than 15 days ago in
/path/ but not in the subdirectories under
/path/? I think it's a perfectly valid use case.