think about the 2d equivalent - a ball rolls down a hill because the potential gradient directs it that way. a ball sitting on a flat pedestal isn't being pulled in every horizontal direction at once by some forces that are proportional to the height of the pedestal. it's not being pulled horizontally at all

there is zero space-time curvature within the sphere, it's "flat", so there's no force. nothing is "cancelled out", force is the derivative of energy with respect to space. it's like a 3d pedestal (or rather, a cylinder excavated from the earth with a flat bottom)