Inrush Current Limiting
This page has a simplified discussion of inrush current limiting for a large brushless motor on electric bicycles.
http://www.ecospeed.com/motdet.html
Note there should be three figures, since the case where there is no current limiting in the early RPM range is described but not sketched.
These principles are appearing in the Dyno results posted by John and others. It appears the lower power motors have higher coil resistance and do not use inrush current limiting, while high power motors have very low coil resistance and employ some form of inrush current limiting. The reason is not just to get the efficiency up at low RPM, but may also serve to protect the MOSFETs and motor coils from thermal damage due to excessive current flow.
In racing when you limit inrush current, you also limit torque. If traction is available you limit acceleration on the track. This can be a benefit to match torque to available traction and reduce wheel spin, or a detriment if the tires support more g-rate acceleration than the motor generates at the drive axle.
I've added Figure 1 to discuss the slick condition on the first lap on the Velodrome. My model assumes traction would support 2 g's, but suppose the slick track supports only 1.2 g's. You would pick up at less than full throttle and ramp up the throttle as RPM increase in a straight line, supporting 1.2 g's acceleration at the drive axle with the current/torque output approximately flat as shown. You would hit full throttle (8.2V PWM) at the point of the knee in the curve, and then the reverse voltage in the motor would continue to increase, limiting the current draw from the battery, the output torque of the motor, and the g-rate of acceleration drops as RPM increase from there. In the time-based response these impacts are exponential curves.