How to make sense of speed vs Torque curves in speed control mode
Speed/torque curves tell you what the motor hardware will do.

Your closed loop controller can control anything it's been programmed to control, within the boundaries set by the motor speed/torque curve.

Consider how you'd drive a car. You could test it with several constant throttle openings, and measure its speed on different inclines, to get a set of speed/gradient curves. However, when you sit in the driving seat and close the control loop, you can choose to drive it at any speed within the speed/gradient limits of the hardware you're controlling.