I'm not taking into account centripetal acceleration, but it is small in ordinary planets. In order for the planet to actually be a torus, it needs to be spinni

I'm not taking into account centripetal acceleration, but it is small in ordinary planets. In order for the planet to actually be a torus, it needs to be spinning extraordinarily quickly, precisely because gravity does not help maintain the torus shape. From my reading, the author's simulations presupposed what s/he believed the gravitational field is. (This is actually a reasonable thing to do, and I don't fault him for it.)