A torus is not a hollow sphere. The OP's article stated that the computed surface of the torus was an equipotential surface, meaning that the apparent gravitati

A torus is not a hollow sphere. The OP's article stated that the computed surface of the torus was an equipotential surface, meaning that the apparent gravitational force (a combination of actual gravity and centrifugal force) at every point on that surface is straight down into the ground. OP even calculates the strength of the apparent gravity at every point on and around the torus. Assuming the planet started out in this toroidal shape, it would be stable since the net force at every location is "straight down", so there would not be anywhere where pieces would just fly off into space.