He means top or over spin. This will result in a lower flight and generally more roll out. At some courses this can give you a longer drive but if carry is an issue then you can't use this technique. I find that with my driver (R11), I can get more distance by using about 1/2 backspin when the wind is behind me on St Andrews, Kiawah and RSG. At other courses I use full b/s on all my drives with no wind or wind behind. Once in a while I will take all the spin off to get a little more roll but I'm not sure the decline in carry distance is fully offset by a little more roll.
I have noticed that since we moved back at STA, the driving for me is less. I rarely bust out a 350 yard drive while before I hit those all the time there. Part of it is the mounds and ridges that seem to be right where our balls land. To get a really long drive at STA you need to land on the back side of a mound which results in those 400 plus yarders.