When printing multiple materials via the wizard, there is one tool change with each layer. However, when printing one material for support and one for the main object, there are two tool changes per layer, doubling the size of the prime pillar.
With Multi Material Wizard and 2 extruders, two layers of each material are printed like when alternating between islands which allows one tool change per layer. When printing support (even dual extrusion support), the main object is strictly alternated with support in each layer and there are two tool changes per layer.
If the support material was treated as a separate island, this would reduce the prime pillar volume by 50% for printing with support material.
