One common misconception when talking about synchro devices is the thought that the rotor and windings signals have a phase shift between them. Although spatially the stator windings are 120O apart from each other, the signals are all completely in-phase or 180O out of phase with the rotor signal.
This misconception most likely stems from 3-phase power where delta-wye and wye-delta transformers induce a phase shift to the signals. It’s good to remember that transformers inherently don’t have any major effect on phase; and that the shift comes from using line-line signals. When monitoring the signals of a synchro with respect to the same ground, you’ll see all of their zero-crossings line up!