That's all we can see about these options in recent enough code:

[openxs@chief percona-xtrabackup-2.2]$ grep -rn sshopt *
storage/innobase/xtrabackup/doc/source/innobackupex/innobackupex_option_reference.rst:239:.. option:: --sshopt=SSH-OPTIONS
storage/innobase/xtrabackup/doc/source/release-notes/2.0/1.9.1.rst:41:  * When using --remote-host to a non-standard SSH port, the |xtrabackup| wasn't passing the correct port to both ssh and scp, which use different options for port number (-p vs -P). It's now possible to pass custom SSH options to innobackupex, such as a non-standard port, with the --sshopt option. Bug fixed: :bug:`733658`  (*Sergei Glushchenko*).
[openxs@chief percona-xtrabackup-2.2]$ grep -rn scpopt *
storage/innobase/xtrabackup/doc/source/innobackupex/innobackupex_option_reference.rst:227:.. option:: --scpopt = SCP-OPTIONS
[openxs@chief percona-xtrabackup-2.2]$ grep -rn remote-host *
storage/innobase/xtrabackup/doc/source/innobackupex/parallel_copy_ibk.rst:38: This option cannot be used together with :option:`innobackupex --remote-host` or :option:`innobackupex --stream` options.
storage/innobase/xtrabackup/doc/source/release-notes/2.0/1.9.0.rst:33:  * ``xtrabackup_binary`` was not included in tar archive when streaming, instead it was written to the current directory. This could cause backups with ``--remote-host`` to fail. Bugs Fixed: :bug:`723318` (*Alexey Kopytov*) and :bug:`787988` (*Alexey Kopytov*)
storage/innobase/xtrabackup/doc/source/release-notes/2.0/1.9.1.rst:41:  * When using --remote-host to a non-standard SSH port, the |xtrabackup| wasn't passing the correct port to both ssh and scp, which use different options for port number (-p vs -P). It's now possible to pass custom SSH options to innobackupex, such as a non-standard port, with the --sshopt option. Bug fixed: :bug:`733658`  (*Sergei Glushchenko*).
storage/innobase/xtrabackup/doc/source/release-notes/2.0/1.9.2.rst:13:Option --remote-host for |innobackupex| has been deprecated in favour of the --stream option and it will be removed in future versions.
storage/innobase/xtrabackup/doc/source/release-notes/2.1/2.1.1.rst:20: After being deprecated in previous version, option :option:`--remote-host` has been completely removed in |Percona XtraBackup| 2.1.
storage/innobase/xtrabackup/doc/source/release-notes/2.1/2.1.0-alpha1.rst:22: After being deprecated in previous version, option :option:`--remote-host` has been completely removed in |Percona XtraBackup| 2.1.
storage/innobase/xtrabackup/doc/source/release-notes/1.6/1.6.6.rst:7:Option --remote-host for |innobackupex| has been deprecated in favor of the --stream option and it will be removed in future versions.
storage/innobase/xtrabackup/doc/source/release-notes/1.6/1.6.5.rst:20:  * When using --remote-host to a non-standard SSH port, the |xtrabackup| wasn't passing the correct port to both ssh and scp, which use different options for port number (-p vs -P). Bug fixed: :bug:`733658`  (*Sergei Glushchenko*).
storage/innobase/xtrabackup/doc/source/release-notes/1.6/1.6.7.rst:12:  ``xtrabackup_binary`` was not included in tar archive when streaming, instead it was written to the current directory. This could lead to a wrong xtrabackup binary being used when preparing backups created with the :option:`--stream` or :option:`- remote-host` options. Bugs fixed :bug:`723318` and :bug:`787988` (*Stewart Smith*).
[openxs@chief percona-xtrabackup-2.2]$