en.wikipedia.org/wiki/The_Man_Who_Skied_Down_Everest

Contemporary mountaineering sources distinguish two different Japanese expeditions on Everest in 1970.

The American Alpine Club’s 1971 summary of the Mount Everest Ski Expedition says there were "two Japanese expeditions at the same time" and that the ski group "lost six Sherpas" in the Khumbu Icefall; it does not describe a Japanese member of that ski group dying of a heart attack. Instead, it says "a seventh died of exhaustion."

A separate official report, reprinted in the Himalayan Journal, is for The Japanese Mount Everest Expedition 1970 and explicitly says the Japanese Everest Skiing Expedition 1970 "had no relation with our organization." That report then states that Kiyoshi Narita of that separate Japanese Mount Everest Expedition "died of an unexpected heart attack."

So the article’s wording is incorrect because it folds Narita’s heart-attack death into the ski expedition described by the film, when the cited expedition report places that death on a different Japanese Everest expedition.