en.wikipedia.org/wiki/Khumbu_Icefall

Authoritative sources distinguish Miura’s 1970 partial/attempted descent from the first successful ski descent of Everest.

• Guinness World Records says Davo Karničar "skied from the summit of Everest to Base Camp" on October 7, 2000 and was "the first person to achieve this feat." That directly contradicts the claim that Miura was the first person to successfully ski down Mount Everest.
• A separate Guinness profile on Miura says that in 1970 he "skied around 4,200 ft down Everest," which shows he did not complete the mountain-wide descent later credited to Karničar.
• National Geographic likewise says Miura attempted to ski Everest from just below Camp IV on the South Col in 1970, and that the mountain "finally saw its first successful ski descent" in 2000 when Karničar skied from the summit to Base Camp.

So Miura was an important pioneer of skiing on Everest, but he was not the first person to successfully ski down Mount Everest in the sense used by reliable historical sources.

The article’s parenthetical explanation misdefines bergschrund.

Reliable reference works define a bergschrund as a deep crack/crevasse near the head of a glacier, where moving glacier ice separates from more stationary ice above. For example:

• Cambridge Dictionary defines it as "a deep crack near or at the top of a glacier, separating moving ice from ice that is not moving."
• The Avalanche Center glossary similarly defines it as "a large crevasse at the head (top) of a glacier."
• Britannica’s definition also describes it as a crevasse and gives the German sense as "mountain crevice," not "iceberg shoulder."

So the phrase "iceberg shoulder" is not a correct definition or translation of bergschrund.