The temporary stretch cavity is a factor in wounding. Nerves, blood vessels, arteries, muscle tissue etc. are stretched and torn to one degree or another (based on a variety of factors) which do effect the severity of the wound.
Fackler and others bent the stick too far during the course of their debates, when they said the so called temporary cavity was not a factor. They were correct in insisting that the only thing that could be counted on though was the direct path the bullet took.
Both the mass of the bullet and it's velocity and energy are factors.