The below is taken from the Harpers Weekly obituary for P.G.T. Beauregard, also known as "The Little Napoleon", "The Little Creole" and "The Great Creole".
Doesn't this clearly show that people new the difference between a "white Creole" and those of mixed-blood?
"Beauregard was born in New Orleans, Louisiana to a white Creole family. He trained at the United States Military Academy at West Point, graduating in 1838, and excelled both as an artilleryman and military engineer. He served as a major under Winfield Scott during the Mexican-American War."
I think you should be very careful in assuming that all references to "Creole" outside of Mississippi and Louisiana automatically means of mixed-race, specifically African.