That curve is a step response curve of motor speed. No motor can respond to that without lots of error (no motor can accelerate instantly).
A CNC controller would keep acceleration and speed within reasonable limits so that the motors have a chance to do what they're told. Then you won't get such a big following error.
Step response curves are useful to set the PID controller parameters, though.
I'm not sure how big following errors one can expect from a well tuned real life machine. If anyone knows, it would be interesting to know.
Arvid |