This is pure horse manure... The much more likely scenario is that he was so nervous he missed the hog completely. When hit in the skull by my .308 the pig goes down like a sack of bricks, and afterward, the skull feels crunchy and deformable through the skin. Scrambled brains inside.
I have killed ~5 with the .308, and about 6 more with a knife (6" blade, good handle). The knife kills were not after being shot, they were hogs that the dogs had stopped and I waited until a dog on the other side had the pig's attention and stabbed it in the heart. One of those nicked my thumb with a tusk, but I ate him for launch instead of the other way around.
Were any of those through the top of the head?
Guess you were there and know better.
A .308 has almost twice the ft/lb of energy of a 30-30. It’s apples and oranges.