It is one of those terms that is tossed about and has been for so long there hasn't been a lot of focus on just how it is applied. It's like "Native American" . That term seems to mean at times, full blood when it may include others such as half blood.
As far back as I can remember, the main requirement for a Creole is Spanish or French blood. Then, depended on where they were as to the accepted mix of anything else. Louisianna has always been different from the way the word is described here and in Mobile. My Caro line has been listed in articles on the Creole family lines here. I don't think we have any French. I do not know who the real 'expert' is who made the distinction or how they decided on the formula.