In a way I agree with what you are saying, that the differential new skills that a PhD provides over a Masters is the ability to invent new knowledge and/or ass

In a way I agree with what you are saying, that the differential new skills that a PhD provides over a Masters is the ability to invent new knowledge and/or assess the claimed new knowledge of others. But, to get a PhD, you have to get a Masters first (or do Masters equivalent work in the first 2 years of your PhD program). In effect, once someone has a PhD certificate, they can throw away their Masters certificate, since the PhD certificate guarantees that they also have sufficient breadth of knowledge + new-knowledge-invention skills.