I don't think there is such a thing as a 100% Savannah...yet. Was the sire an SBT? In that case he has 3 generations of only Savannah to Savannah crossings in his background. But guaranteed he does have some other breeds used along the way, whether that is Bengal, OS, DSH, Maine Coon, and others. Your leanings toward an OS look probably was a factor in choosing your babies...surely you are thrilled with them, no matter the background?
Don't be offended when people ask about your "bengal", lol! I get that too, and when I correct them, they always reply they have never heard of a Savannah. In my neck of the world most people have never even heard of a Bengal
Look at it as your golden opportunity to educate them about the differences between the two spotted breeds