Dyno plots are a necessary evil (sigh). Everybody wants to see them, few know what they're looking at, understanding one is far more than can be explained in a forum post or two.
In short, they're adjustable and valved for their intended uses.
FWIW, all but one of the Xida kits sold have gone to someone that has test driven them on street, track or autocross.
Running the ring, you would definitely want the optional double spring set up. You would be fine with the singles but the doubles would give you some extra adjustability for dealing with the compressions and mid turn bumps in the high speed heavily cambered sections. Also nice to be able to fiddle with compression for wet weather.
If you just wanted to valve for Spa and the 'Ring, we could raise the knee point of the compression a bit on the singles to suit. The drawback to that is the ride at lower speeds on rough public roads would suffer noticeably. Only at speed would it smooth out and start floating over the rough stuff.
The doubles allow you to quickly and more finely adapt to a broader range of conditions.