Yes, if any presuppositions are allowable, then you can end up with any conclusion you want. The unity of individual consciousness appears to be a more fundamental concept than any physical theories, since all physical theories are evaluated through said consciousness. Thus, any physical theory, such as forking consciousnesses, that make the unity of consciousness absurd, and thus undermines its evaluative capability, undermines the physical theory itself. Like Darwin's doubt of how we can trust the thoughts of a mind evolved from monkeys.