The motto on the VC is “For Valour”, not “For Gallantry”. Originally it would have been “For The Brave”, but the story runs that Vicky didn’t want to imply that any of her soldiers weren’t brave. As for the CGC, presumably garden-variety gallantry is expected (though it may be rewarded with a Mention in Despatches) and you have to be noticeably more gallant before anyone makes a fuss about it.