The historical reality is somewhat more mundane and more instructive.

The code worked not because of any mystical property of the Navajo language but because of the specific historical circumstances that made it inaccessible to the specific intelligence service it needed to defeat.

Japanese signals intelligence had virtually no access to Navajo language resources.

There were essentially no Japanese speakers of Diné Bizaad, no significant academic literature on the language in Japanese, and no historical relationship between Japan and the Navajo Nation that would have created such resources.

The combination of an unfamiliar language and a purpose-built code added on top of it created a communications system that was practically unbreakable in the timeframes that battlefield intelligence required — not because it was theoretically unbreakable, but because breaking it would have required resources that simply did not exist.

This is not a criticism of the Code Talkers or a diminishment of the code’s effectiveness.