I think some people are missing the point here.
The pathologist surely didn't mean to say that it was the actual rate of climb that caused the stowaways to die. Rather, he was referring to the fact that, although the human body can survive at high altitudes, it can only do this if it is allowed to acclimatise to the lower oxygen levels. Being taken up to that altitude at any rate achieved by an aircraft, be it military or civilian, does not allow the body to acclimatise and therefore the victim will suffocate (hypoxia) probably before freezing to death (hypothermia).
I understand that climbers who try to climb Everest allow themselves a week at the higher camp to become fully acclimatised before they attempt the summit.