In my opinion the turbines area is very large in regard to the wing area, above all for the M600, probably due to E-VTOL requirement as previously discussed.
So during the flight lowering the thrust coefficient of the turbines is needed in order to keep a L/D ratio high enough. The used means can be the pitch or stall like for wind turbines working at high wind speed. In the same time that can also avoid an excess of rpm. In the other hand generators have to be bigger and heavier due to the required higher diameter of the turbines.