The throttle pedal has a small circuit boards that purposefully dampens and slows the throttle position signal to the ecu.
ie. If you press the throttle 50% instantly, the throttle pedal circuit may take a second to go from 0% to 50% in terms of the signal sent to the ecu.
A throttle controller will also see that signal that goes to the ecu but here is the kicker
If you have the controller on maximum response, it will for instance send 100% signal to the ecu when the throttle is sending 5%. It uses clever algorithms to work the signal sent to the ecu back to the actual throttle position. The higher the controller setting, the more aggressive the response.
I have installed one, and the "feel" to me is better than a mildly chipped engine. And a throttle controller is less than half the price of a chip/flash/remap, without the risk of damaging the engine as the ecu is not tampered with and keeps all the safeguards.
The reason the OEM doesn't do it from factory is that smooth throttle application is p[referred by the general public who can't drive properly, have no interest actually in cars, and will "lurch" around otherwise.
