At a certain point the roughness of the ball reaches a size threshold where the imperfections are smaller than the wavelength of light, and the surface takes on a glassy smoothness. Intelligence has similar milestones, almost like phase changes, I think, where capabilities are reached. Maybe it's like a superposition of many small step functions.
intelligence is more like polishing a ball smooth than growing the ball to infinity.
For many tasks, it will be smooth enough.