When you use the Maneuver type "Speed Profile" you must understand that the IPGDriver model is still active. Using the input that we specify in the input file, we aren't overwriting the vehicle's velocity entirely, we're just setting a target speed. The driver will try to follow the target speed whilst still regarding various environmental influences and - most importantly - under consideration of the vehicle's physical limits.

You can imagine the speed profile functionality as a series of speed limit markers that the driver tries to follow very carefully, an identicle course of target and actual velocity is not guaranteed.