This example actually uses vector control. The controller takes the current of the three phases of the stator and the angle of the rotor as inputs. Using the Park transformation, the 3 currents are mapped to the direct and quadrature axis currents id and iq respectively. The controller regulates the current of the quadrature axis to provide the required torque. In pe_pmsm_drive/PMSM controller/Feedback controller, the cross paths between id and iq cancel the natural cross coupling between id and iq, so that they can be controlled independently.
To better understand the control method, I suggest you take the equations of the PMSM which you can find here https://www.mathworks.com/help/physmod/sps/ref/permanentmagnetsynchronousmotor.html
and see what happens when vd and vq are equal the values calculated in pe_pmsm_drive/PMSM controller/Feedback controller at the output of the add blocks which follow the d-axis current PI and q-axis current PI respectively.
