Or they just re-used the format because it already exists and works perfectly well. Don't forget, the "format" in question is just a 16-byte header, it's trivia

Or they just re-used the format because it already exists and works perfectly well. Don't forget, the "format" in question is just a 16-byte header, it's trivial enough that it would actually be more effort to come up with a brand new format (with absolutely no benefit) than to just re-use the existing 16-byte header definition.