Immortality is here and now. Ok!
Even Buddha left his body but he is still immortal.
What he meant is the same. Even a fictional character becomes immortal, for once in a while. For example James Bond is having such a long youth. He ia still portrayed young. But as per Buddha, nothing is permanent, everything is impermanent and permanent at the same time. Just as light is nothing without dark, permanent is nothing without impermanent.