Why did the Royal Navy pronounce Athabaskan differently?

Why does the wartime Royal Navy pronunciation of Athabaskan differ from modern Athabaskan usage?

The earlier pronunciation followed a 1944 Royal Navy phonetic guide, while modern Athabaskan speakers use a different pronunciation.

A viewer from Alaska notes that Athabaskan speakers do not pronounce the name as it was said in the earlier video. The wartime rendering came from a 1944 Royal Navy style guide that supplied phonetic pronunciations for ship names. That document records how sailors were instructed to say the name at the time, rather than settling how the people named pronounce it now. Comparing the period guide with modern usage can reveal how the Navy adapted Indigenous names and how pronunciation changed after the war.