Looking at the rotor head there appears to be no provision for cyclic control of the head. Even though the collective would be fully down there should still be space for rotor control but the star seems to be in positive contact.
It is possible, just possible, that they tried using just collective inputs for the head and differential tail rotor control for manoeuvering.
Sikorsky had a similar arrangement with his first experiments though the rotors were to augment, not control, the main rotor.
It would not have been very successful as there would have been too many problems with inflow roll.