Depending on type, the controls might not be rigid, but tending to stir the pilot's arms around the cockpit due to unopposed aerodynamic feedback forces.
But as the hydraulics are main rotor gearbox powered, with full system pressure being available at very low rotor rpm (well below the limits supporting flight), it's unlikely to be a relevant factor. In any event, a pilot suffering a double hydraulic failure would hardy switch off both engines.