Helicopters create a massive amount of torque from the main rotor. It wants to twist the whole aircraft, like revving the engine in a car with a big V8. That is one purpose of the tail rotor, to prevent the body from starting to rotate opposite of the main rotor. Look up a video of a helicopter with a failed tail rotor.
But the torque from the main rotor varies, depending on whether the pilot is increasing or decreasing power. The pilot has to constantly adjust the amount of power going to the tail rotor to match the amount of torque from the main rotor. But the power can’t be a set percentage of the main power, because the tail rotor also has to be adjusted to allow the aircraft to rotate to change direction, and to compensate for wind direction, if flying parallel to the wind or in a crosswind.
In this design, the rotors are turning in opposite directions, so their torque cancels out without need of a tail rotor. I think intentional rotation is accomplished by varying the power between the two rotors somehow. Not having to compensate for the torque of the main rotor makes flying the aircraft slightly less complex for the pilot, at a tradeoff of more mechanical complexity.