"This  parameter can be used to ensure that if default acls exist
              on parent directories, they are always honored when  creating  a
              subdirectory.  The default behavior is to use the mode specified
              when creating the directory."

The problem is in the sentence "The default behavior is to use the mode specified
when creating the directory". It can mean two semantically AND syntactically
different things:
1) The defaut behaviour when creating the directory is to use the specified mode
2) The default behaviour when creating a subdirectory is to use the mode that
was specified when the parent directory was created.