To make the transition from cruise to autorotation may be impossible. The retreating blades must make the transition from 100% reverse velocity to 100% conventional velocity. At some point during the transition, the positive lift on the retreating side will be offset by an equal amount of negative lift on the same side. Since there must be bilateral symmetry of lift, all lift must therefore be removed from the advancing side. During this time, only the front and rear quadrants will be contributing to the lift and to the rotation of the rotor.
In addition, the speed or the rotor must be increased from 50% NR to 100% NR. The rotor may well be unable to support the craft from only two quadrants, while also having to increase its rotational speed at the same time.
PS. They added wings on later sketches.
More, if interested.