command line help doesn't list options found in man page

Binary package hint: util-linux

The man page lists additional options not reflected in the command line --help output, specifically options -d and -l.

$ umount --help
Usage: umount [-hV]
       umount -a [-f] [-r] [-n] [-v] [-t vfstypes] [-O opts]
       umount [-f] [-r] [-n] [-v] special | node...

SYNOPSIS
       umount [-hV]

       umount -a [-dflnrv] [-t vfstype] [-O options]
       umount [-dflnrv] dir | device [...]

ProblemType: Bug
Architecture: amd64
DistroRelease: Ubuntu 9.04
NonfreeKernelModules: nvidia ath_hal
Package: mount 2.14.2-1ubuntu4
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: util-linux
Uname: Linux 2.6.28-11-generic x86_64