Graybeard, no need to be amazed, it is a fact. Yes bullet design has a lot to do with penetration, but you still need velocity to drive that bullet. I am not saying it has to be hyper speed to accomplish it. There is never a science to this, there are just to many variables involved for it to be cut and dry. My experience is on game in the field, not what I read. I take the time to do my own research and not just pull information from my back side.
I have shot many game animals with handguns, a lot up close and some at further distances. I have recovered many bullets and I have had some complete pass thoughts. But to think that if both shoulder are shot through, that you are going to have a bullet exit all the time is just not a good bet. I shot a black bear at 25 yards with my 500 mag with a 370 gr. hard cast bullet. The bullet on impact of the opposite side shoulder fragmented the bullet, half of the bullet exited and the other half was found in the shoulder bone. Did the bullet have to exit to be effective, no the bear was dead on the spot.
The bottom line here is, pick the right bullet and velocity and most impotent, SHOT PLACEMENT! Also know the anatomy of the animal you are shooting.