xfce4-session-logout has long and short opts (https://git.xfce.org/xfce/xfce4-session/tree/xfce4-session-logout/main.c) Short 'h' opt is duplicated in sources with 'hibernate' and 'halt'. It should be removed from both and moved to 'help'
Eric Koegel referenced this bugreport in commit 1ed67a56974a32ea01dcb1fabc85b95238025cc8 xfce4-session-logout: deconflict -h option (Bug #12806) https://git.xfce.org/xfce/xfce4-session/commit?id=1ed67a56974a32ea01dcb1fabc85b95238025cc8
The --help option appears to come from the g_option_group and I don't see a way to set it to -h so I kept halt with -h and changed the letters of the other options. Marking closed.