This is electric motor field weakening through mechanical means, almost as old as development of the electric motor. It enables the motor to speed up without increasing power, but reducing torque. It enables the motor to behave as having a continuous gearbox attached, able to configure from for low speed, high torque to high speed and low torque. Now-days there are electrical control means of field weakening that don't need mechanical encumbrances, easy to implement especially at such low rpm ranges as needed for a propeller.
Looks like a highly complex and failure prone solution in search of a problem that was solved decades ago.
Reminds me of a series of old books I inherited from my dad - these detailed clever mechanical devices (hinges, power transmission, articulation, etc) that solved all kinds of problems back in the day. Looking at the books today, one realizes almost every single one was made obsolete by stepper motors and a computer to position them.