I think the in-game FAQ is for SA only... not for war or Battle for EC, whatever GREE calls war now.
However... In Kingdom Age (KA is not CC, but what's the diff? all of GREE's apps are similar, mostly), I tried joining a guild, requested to join, and a pop-up stated to wait until the event was over before requesting. I also tried to leave a guild with another KA acct, same pop-up: wait until event is over. KA has their 3-day war going on now just like CC does... oh joy.