This scenario is one possible projection; it assumes the eventual development of a subduction zone in the West Atlantic that would overcome the spreading at the mid Atlantic ridge, eventually sealing the basin. I don’t understand the mechanisms well enough to know how that prediction was made, so someone with more experience on the subject can chime in.
That stood out to me, too; I wonder if that model assumes the shrinkage of the Pacific reverses when the Atlantic starts to close. strange. I also didn’t see them try to account for the rifting in Africa, perhaps they assume that will fail to complete like the North American one did