People make that mistake often. Sub saharan just means below the sahara, while Volta is in fact sub Saharan, it is a very small area compared to the rest of the continent. I think the only way you'll be able to tell is in the long run. When the snake gets a few years old and it seems very heavy, and longer than what might be considered "average", then you might have a good idea if it is in fact from that area or not