You're right Richard, it must be making quite a difference. I know from my experience that if the trailer starts to misalign that you have to steer the cab quite a bit to correct when reversing, more than what Jean Claude would be able to compensate for and he seems to be frozen once they separate. Here's what Volvo has to say about the system.
The Volvo Dynamic Steering system adds an electronically controlled electric motor to the steering gear, which retains hydraulic power assistance. The system is designed to give additional assistance at low speeds, reducing strain on shoulder and arm muscles. The system provides self-centering action in reversing maneuvers. Conventional truck power-steering systems require constant steering correction over heavily cambered roads and when driving in cross winds. The Dynamic Steering system automatically compensates for these conditions, allowing the driver to steer straight ahead. The system also reduces the steering correction needed when driving over surface cracks and potholes.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.