Rapid Miner Accelerator - for Direct Marketing

I had a couple of questions on the process design underlying the RM Accelerator for Direct Marketing, Hope someone can help. I am trying to learn the tool and see if I can build upon the DM accelerator.

a) What is the purpose of the Default Precision process (it is a sub-process)? I sort of understand what it does. But not sure why it is required?

b) What is the purpose of the Last Model operator - why not simply connect the model to the data set with missing "label" vaues and get the predictions

Thanks