Unless all the medical (vet) facts that have been taught in higher institutions to people who were to become and did become medical doctors and surgeons of animals, are proven to be incorrect, I will have to go with a skill and expertise that greatly surpasses bowhunting opinions.
Holding with the medical facts until the facts are proven to be corrupt, I would then assume that a shaft that enters the fabled " hollow spot" is nothing more than a shot that went bad and did not hit a vital organ that causes immediate or soon death, but death may occur within a day or two.
PS:
mr4pt, you have a list of those " thousands of bowhunters?"