A more accurate description of --force as I know it.

rsync.yo

@@ -489,11 +489,13 @@ then use the --delete-after switch.
 dit(bf(--ignore-errors)) Tells --delete to go ahead and delete files
 even when there are IO errors.
 
-dit(bf(--force)) This option tells rsync to delete directories
-when non-directories (for example symlinks or plain files) take their
-place even if the deleted directories are not empty.  This applies to both
-the --delete option and to cases where rsync tries to copy a normal file
-but the destination contains a directory of the same name.
+dit(bf(--force)) This option used to alter the behavior of the --delete
+option to force deletion of non-empty directories, but that happens now
+anyway because rsync does deletes in depth-first order.  The only known
+difference that --force makes now is an obscure case where the source is a
+non-directory (for example a file or a symlink) but the destination is a
+directory that contains a directory by the same name as the source while
+--recursive mode is in effect.
 
 dit(bf(-B , --block-size=BLOCKSIZE)) This controls the block size used in
 the rsync algorithm. See the technical report for details.