It isn't overriding. You can write the model logic in Process Flow easier. You bypass some structures or methods. But you are still free to adapt the same structures of the 3D into Process Flow. For example take the tasksequence in 3D. A tasksequence contains the action the operator will do before he gets the job to do. In Process Flow you can set for each activity equal to a task an option to wait until complete. Thus you can control the action of the operator while he does the sequence. Some user might argue that you can achieve the same in 3D, too. But it is much more code over several triggers distributed.
