Good point, but I wouldn't be arguing the minutae of ballistics with Dirty Harry pointing his S&W at my head. 'Dead' is close enough to 'most poweful handgun in the world' at that point.
If it were me lying there, he could have just as well been saying "This is a .22 short, the weakest handgun in the world. It'll give you a really bad headache..." and I probably would have left the shotgun by my hand alone. :-)
The author was talking about defensive rounds. He was saying how a 25 auto is compact to carry but anemic.
Anyway, he referenced where a perp was holding up a victim. The victim didn't move fast enough so the perp shot him in the head.
The bullet went into the victim's scalp but didn't penetrate the skull. It just zipped around the scalp along the contour of the skull.
The victim was treated and released with no more than a really bad headache.