That's my question. according to International Organization fo Standardization

ISO 4217 Currency codes

"This standard establishes internationally recognized codes for the representation of currencies that enable clarity and reduce errors. Currencies are represented both numerically and alphabetically, using either three digits or three letters. Some of the alphabetic codes for major currencies are familiar, such as “EUR” for Euros. Fortunately, ISO 4217 covers everything from Afghanis to Zambian Kwacha as well."

Definitions and the practical application of them seem to be at least arguably not the same thing.