That means absoutely nothing. A single bullet situation proves NOTHING. People have been hit with all kinds of great preforming bullets that did not live up to the expectations. The difference between a solid hardcast and a solid softer bullet is marginal.
Maybe you should explain that to the victim's families, the Medical professionals, the Firearms Examiners et al. You might be on to a real break-thru in the study of Terminal Ballistics. Later.