the claim is that it's the perfect shape for delivering glaze. assuming the interior of a torus does not contact the tongue, i submit that a torus wastes glaze, and the spherical shape is indeed perfect for delivery.

That holds if we assume a frictionless digestive tract that performs no action on the cereal. Since the cereal will be crushed in the mouth, and all parts mushed together, it's reasonable to assume that the inner radius of the torus will touch the tongue, and what's more, the original claim was never about touch the tongue, but delivering more glaze in the same volume.