One shot stops from solid hits from an effective .40S&W load do occur more frequently than for lesser powerful loads and are not a myth. But just like most everything in life, there are no guarantees. Defensive handguns are just not that powerful to begin with. They are certainly much better than a hammer, but when compared to a main battle rifle of say .308 caliber.. of course, bet on the rifle.
There is too much detail lacking to make a reasonable assumption from this article. How did the bullets perform once in the body? Did proper expansion take place? Was sufficient tissue disrupted and destroyed with the early hits? And on and on.
What this article does prove is that the old adage that, "anything can and very well may happen" is correct. It also backs up the argument to continue to research the latest offerings in ammunition and use the best you can for your sidearm. Then make your hits count as best you can.