That's like you can't deduce the input t from a cryptographic hash h but the same input always gives you the same hash, so t->h is deterministic. h->t is, in practice, not a way that you can or want to walk (because it's so expensive to do) and because there may be / must be collisions (given that a typical hash is much smaller than the typical inputs), so the inverse is not h->t with a single input but h->{t1,t2,...}, a practically open set of possible inputs that is still deterministic.