The only thing I can think of is that the Polo rack fits under the fuel tank, and maybe the golf not.
You have to Alex, he sells the brackets on here, maybe he know this.
I found a plausible explanation:
the main reason is that in a golf (and in a Porsche and ...) the lower control arms are almost the exact same size as the tie rods, thus it doesn't matter how short they are, the bump steer is almost nothing.
This doesn't go for a beetle/karmann and therefore a R&P with the bracket in the midle of the car and long steering rods compensates the bump steer as much as possible..
Glauco