Autossh 选项与其手册页中的内容不一致？

我有一个幼稚的问题，但是通过阅读这个线程，例如：https ://superuser.com/questions/37738/how-to-reliably-keep-an-ssh-tunnel-open

可以在接受的答案中看到如何使用autossh，例如：

autossh -M 20000 -f -N your_public_server -R 1234:localhost:22 -C

但是从autossh https://manpages.ubuntu.com/manpages/focal/man1/autossh.1.html的手册页我只能看到 3 个可用选项-M：-f和-V.

在我的系统上同样的事情：

$ autossh --help
/usr/lib/autossh/autossh: invalid option -- '-'
usage: autossh [-V] [-M monitor_port[:echo_port]] [-f] [SSH_OPTIONS]

    -M specifies monitor port. Overrides the environment
       variable AUTOSSH_PORT. 0 turns monitoring loop off.
       Alternatively, a port for an echo service on the remote
       machine may be specified. (Normally port 7.)
    -f run in background (autossh handles this, and does not
       pass it to ssh.)
    -V print autossh version and exit.

Environment variables are:
    AUTOSSH_GATETIME    - how long must an ssh session be established
                          before we decide it really was established
                          (in seconds). Default is 30 seconds; use of -f
                          flag sets this to 0.
    AUTOSSH_LOGFILE     - file to log to (default is to use the syslog
                          facility)
    AUTOSSH_LOGLEVEL    - level of log verbosity
    AUTOSSH_MAXLIFETIME - set the maximum time to live (seconds)
    AUTOSSH_MAXSTART    - max times to restart (default is no limit)
    AUTOSSH_MESSAGE     - message to append to echo string (max 64 bytes)
    AUTOSSH_PATH        - path to ssh if not default
    AUTOSSH_PIDFILE     - write pid to this file
    AUTOSSH_POLL        - how often to check the connection (seconds)
    AUTOSSH_FIRST_POLL  - time before first connection check (seconds)
    AUTOSSH_PORT        - port to use for monitor connection
    AUTOSSH_DEBUG       - turn logging to maximum verbosity and log to
                          stderr

和选项从何而来-N？我没有找对地方吗？-R-C