The hardest working (structurally) sections of track aren't necessarily the bits where the train is going the fastest - it's more about where the track is required to carry a lot of load - that's subtly different.
As we'll have seen in all the photos, the pull-outs of those drops have lots of supports, meaning that although the train is excerpting a lot of force on the track, the track is transferring most of that straight in to the supports. If you look at the supports on Skyrush they're spaced much further apart. Red Force is a little bit different, as it's much bigger and faster, but the same principles still apply.
So the double spine sections might be for use somewhere where the track has a long span (over a pathway, for example), or where they can't put as many supports in the ground for other reasons (maybe buried utilities or other attractions).