ns is showing you the best name it has for the resource in question. if you did bind /n/ftp/dir /n/tmp, then it can't tell you that you did mount '#s/ftp' /n/tmp because that's not accurate--'#s/ftp' would get you /n/ftp, not /n/ftp/dir.
so it shows you /n/ftp/dir, because that is the name that was used at the time, even if that name no longer means the same thing. russ