I believe that the engine drag is insignificant while the turbine is providing positive power to the compressor N1 N2, (N3).
The majority of the drag is associated with the engine nacelle.
The compressor under power is still accelerating the air as evidenced that the incidence angle on the blades, including the fan is still associated with positive pressure behind the blades (pumping).
This is generally true even at windmill start conditions.