I've always been a bit confused about the interest in this topic. Many cars with automatics went to this after the industry started moving away from carbuerators to fuel injection and computer control. My 1990 535i has one. It's an 18 year old car.

It's simply a switch to tell the computer that you want full, open throttle acceleration in the lowest gear that doesn't over-rev the engine. Nothing magical about it.

I do the same thing in my manual Roadster by downshifting one or two gears and burying the pedal into the carpet.