I think it was a range of different things that made the Golf quicker, some of it power/torque differences on the straights and general suspension setup. I can't remember the exact video, I just remember thinking that stuff seemed too expensive for the gains it brings. I do remember him fiddling with the rear subframe adjustments which made things worse!
I think Nurburgring Apex people use it on one of their M cars as well. I'm sure it's good when dialled in but not sure the differences in the real world vs top tyres, driver skill, and coilovers are justified....but horses for courses I guess.