This is so because until an idea has a physical manifestation, it cannot be perceived in a useful collective manner. Likewise, manifestations have no value unless they can be translated into ideas to be transported, improved and evolved. This doesn't necessarily mean that the artists are satisfied with the fidelity of the finished product to the original vision. Constraints of ability, budget, timelines, and other factors will have modified the vision and the finished product may be quite different. This doesn't imply that the first half excludes collaboration, for quite the opposite is the case.
Collaboration is a necessary component of every stage of the model.
So is independent work. It has already been mentioned that the second half of the creative process creates a new Condition for the first half to act upon. Many of us equate conditions with problems. Nor are they symptoms of problems. This is more than just semantics, and in a sense it embodies much of the philosophy of MG Taylor Corporation.