Looks like its a 16v Mk3 and a 1.8T Mk4. No mention of the other two marques.
Very surprised that a Mk4 with the same bhp but heavier than a Mk3 is faster? 
Fortunately I have the article and all I can say is what an odd selection of Golfs to compare.
Mk1, 1.6
Mk2, 1.8 8v
Mk3, 2.0 16v
Mk4, 1.8T 180PS (Anniversary)
And if you saw the images from the article, the Mk2 looks the softest handler of all and the Mk3 a bit tail happy. But then this is dramatized for an article.
Perhaps if a later Mk1. with the 1.8 engine was used and a Mk2 16v the lap times would have been so much different. If everything was kept 8v then perhaps older would still be better. A pointless test. I hope this brings the thread into line.