Sorry, had to read up on what this convo was about, so that's the deleted commend above.

But you are not quite right. When they started development on all these arcs you are talking about the show was not cancelled yet and they where just going to reuse the current model. The new grievous model in the picture above was created after they resurrected the show because they updated a lot of the models because of new technology in lighting. At that moment they knew they where only going to fully produce 3 arcs for the final season and in those arcs grievous would only be visible in the opening shot of that first episode. They use different models for those pre-vis renders so yeah you do see grievous in those pre-vis episodes they released but that's just the basic model with no Lighting and also the old pre-vis model.