Thats the speculation anyway because they taste similar. There are in fact many old French apples of this type which few people are aware of and any of them could be the parent I would say. Pomme Raisin, Belle Fleur Rouge, Rambour d’Automne, etc all have similar skin, flesh color, and aromatics as Snow and McIntosh. Even the English Worcester Pearmain is probably descended from an old French apple.
In my opinion the most tasty of these is Akane (child of Worcester Pearmain), its a special apple. Too bad it rots so badly for me.