Ah, this just got moved. Copy pasting my post which was a reply to this one :)
Well, a bug would be if the feature was intended to achieve those effects such as half tone dithering and they are not working, but it is not built to achieve that effect which makes it a feature request. On the gradient, depends on what you mean - shadowing and GI are not affected, the Toon shader is changing the Diffuse (direct) and Specular Highlights. This means smooth gradients may still be seen in shadows etc. Since the shader wasn't intended to posterize shadows, this too would be a feature request. But in this instance it could be you mean something else about not achieving cel shading, in which case it might be a bug and then a ticket via
https://support.chaos.com/requests/new would be the way to go.
Much can be done with the current shader though, two examples I've just been messing around with. The core is using CShading_Components with only Direct Diffuse and Reflection enabled, and Indirect disabled entirely. Then there are other things done, such as making the Sun very small, and using a native Max light with no shadows, and a Corona rectangle light with Directionality of 1.
I can't share the scene, but I deleted everything, then played with the lights a little bit with just plane and sphere, placing a Corona Sun, Max Directional no shadows, Max Directional shadows, Max spherical no shadows, and rectangular Corona Light, sample image from that scene is the Corona Sun enabled everything else disabled. Sky was also set to pure black, with a direct visibility override to give it some color.
EDIT just changed the saved scene to avoid the annoying missing textures warning on opening :) PS don't forget to swap to the Components render element view, as there is still some subtle gradiation in the Beauty.
No idea if the light, scene, or material set ups here will let you get close to what you were hoping for, but they might!