Very sad stuff
I do think there's some issues with timelines for the players, unfortunately.
This part:
Stevenson pleaded with the Bruins training staff and doctors not to force him to play, having lost a substantial amount of blood… Stevenson’s pleas were ignored. He was forced to play the night in Fredericton, where he sustained another concussion, risking death due to second-impact syndrome.”
In 1951, boxing regulators in New York, acting partly on the findings of Critchley's study, introduced rules that demanded boxers who were knocked unconscious during a fight had to be sidelined — no fighting or training — for at least a month. After that, boxers could return to the ring only after passing a medical exam. A 1952 study in the New England Journal of Medicine recommended football players end their careers after their third concussion. In 1982, a study in the Canadian Medical Association Journal recommended athletes stay out of competition until headaches and other symptoms had disappeared.
This is somewhat misleading -- the abstract of the 1982 study gives their criteria for assessing a concussion, and even their "mild" definition includes being unconscious transiently. As we know now, concussions don't require a person to be unconscious at all. It looks to me like the argument implies that the NHL should have been ahead of where most medical science was, and part of what makes the argument connect so much today is our current understanding of head injuries, not so much what we understood in the 1990s.