I don't understand what your point is... Zoro went from no CoC to ACoC immediately lol, that's far less believable than Xebec going from ACoC to another level of ACoC.
Xebec clearly had some difficulty with Garling and Co since he started the fight fresh and left the fight bloody. Against fodders, people aren't using all their abilities so it's different. Why would Xebec not use this ACoC ability against Garling when we already know he's using ACoC to hurt him in the first place, makes no sense.