I think this is not a cretical issue since people usually ask the faculty that they r happy with to write recommendation. I don't think this will affect the recommendation much. So it's ur choice. As for my self I waived it!!!
I just thought this give the faculty more sense of comfort writing what he/ she thinks right. By saying that, I don't expect them to write it different if I can read it, but just a sense of comfort. I might be wrong!!!!!