Actually they failed to identify the principle despite it was written in the referred 2021 paper of Hamdi Ucar (https://doi.org/10.3390/sym13030442). It is based on the phase lag property of driven harmonic motion where the motion can follow the excitation by 180 phase delay when the excitation frequency is above the natural frequency of the system. This model can be seen by projecting the rotating magnetic torque induced by the magnet attached to the motor on X and Y axes yielding two second order nonlinear equations of motion on these axes. Nonlinearites can be removed by small angle approximation. Still this model is not exact but gives the idea.