You will typically get the positive Sphinx when you get a positive Spring test. There is one exception though. If you have a bilateral sacral extension, there will be a positive spring test, but a negative sphinx test.
So they are not exactly the same. Both can be used to differentiate between forward and backward sacral torsion/rotation as well as between unilateral sacral flexion/extension. However, the spring test can also discriminate between bilateral sacral flextion/extesion.
Hope that clears it up!👍