I've read that quote, or something very similar, dozens of times over the years and the facts don't agree. All of the typical service handguns 9mm and up tend to be effective the vast majority of the time in actual shootings with good JHP ammo. With old school FMJ they tend to be effective about 2/3 of the time. Caliber seems to be a non-issue and equal shot placement with a rifle is only slightly more effective.
What a rifle does is improve accuracy and range, but at extreme close range the ability to use a handgun with one hand outweighs that.
The best judge of what is effective is a handgun round that you can shoot accurately that will penetrate around 12" in gel along with good expansion. Expansion is good, and more is better unless it starts to limit penetration.