Route6 3-5-4 gearset

[banpei]

I recently came across a trackcar for sale on Yahoo Auctions with a Route6 3-5-4 gearset installed. So I was intrigued by what's so special about this gearset.

I found this posting on Cartune and it basically describes it as reversing the 4th and 5th gears, like this:

In this posting, it described the 5th to be a 3.5, so it's somewhere between 3rd and 4th and it makes sense to swap 4th and 5th. However, I found other Route6 gearsets that retain the 5th overdrive.
What other benefits could there be of swapping 4th and 5th if it isn't a 3.5?