Help for ALLCHAN and ALLCHANL is identical while these commands do differ.
Quoting from http://toxin.jottit.com/xchat_help_commands:
ALLCHAN ALLCHAN <cmd>, Sends a command to all channels on all servers.
ALLCHANL ALLCHANL <cmd>, Sends a command to all channels on the current server.
To reproduce type:
I'm running Debian packaged XChat, Version: 2.8.8-3.1+b1