I think that is still why Kumba is one of the more forcefull traditional sitdown style coasters B&M ever built. The tilt or recline in the seat lowers the riders center of gravity and allows the rider to tolerate g-forces better and also lessens the effect of g-forces because of the lower center of gravity. Then again the reclined seat is much more comfortable for the rider and provides a much smoother experience than the flat seats.
I don't know about your idea. Nitro, which has this tilt is extremely forceful, especially with positive g forces, in the helix, hammerhead and valleys of its hills.
From offride videos of kumba, its apparant that it travels much quicker through its elements than newer B&m loopers. I think this is the reason to account for it being less forceful.