No, this method is not intended to be used in orbit determination, it is intended to be used from the generation framework.
No, it is not sufficient. The problem is that we need to be able to move the satellite a little. See issue 1220 and also the last part of this discussion. In the case of interplanetary mission, we don’t even move spacecrafts “a little” but rather “a lot”, and using shiftedBy is not sufficient, so returning a constant state is even worse.