The problem with "stopping power" is that folks are of the impression it is the power that stops a target. It isn't, of course. Whether or not a target stops depends on MANY things other than power or bullet characteristics...as already noted.
My pet theory is that the expression of "stopping power" was just simply a bubba's way of trying to express in writing that which a bubba could not spell, "terminal ballistics." Unlike stopping power, however, folks do seem to understand that terminal ballistics are about what the projectile is doing at a given time in its flight in regard to velocity, energy, etc. if it were to impact something at a given distance.
In terms of Para Bellum's quote from Ammo Oracle, the anatomy of a deer is NOT substantially different from that of a human.
This is, unfortunately, folly. Deer, to begin with, have SUBSTANTIALLY different anatomies than humans (surprise surprise). The distance in tissue to vital organs is different, bone density is different, the location and strength of CNS structures is different, as is the vascular system. Further, because the CNS structures of deer are somewhat more primitive and less intricate than those of humans, they are far less fragile in some places, far more fragile in others. What works in deer may or may not work in humans. The same goes for hogs, varmints, pigs, dogs, zombies (headshots only please), and aliens (particularly grey skins- go for the big eyes, not center mass).
No doubt, there are differences, but they are subtle, not substantial. An octopus has a substantially different anatomy from a human, but a deer is very similar.
True, the distances between organs will vary as will bone density. Deer are setup for quadrupedal locomotion and humans for bipedal. As for the CNS being more primitive, hence human CNS is more fragile than a deer CNS, NO. Strangle, deer have the same controlling nerves as humans and they are located is close to the same relative anatomical positions. If there is a more substantial aspect to the deer's CNS, it is in the bone protecting it. On the spine, the bone will tend to be more substantial in terms of bone density than what you would find for humans, but the bone around the brain is less dense and there is less of it.
Where the AO is correct is that just because something works in a deer it will work in humans or vice versa. Determining what does not does not work isn't because of substantial anatomical differences, but subtle. Heck you could say that the spacing between the organs and bone density variances made for substantial anatomical differences when you compare a 300 lb footbal player with his 92 lb osteoporotic grandmother.