Not taking anything away from the video or shooting, both excellent but I wouldn't draw a conclusion from those two shots that the 4 bore hits hard. The first shot very much looking like a neck shot, the second buff definitely neck shot if not behind the ear. The 4 bore probably does hit hard, at both ends, but any big bore or even medium bore with those neck shots would have the same effect.
Chest or shoulder shots are what will sort the boys from the men when judging knock down or heavy hitting and the 4 bore should produce the goods, just this video doesn't show that aspect.