The first is about the nature of consensus. The second concerns the differences between the process used in delphi, and some of the simpler processes which are used for reaching consensus. Consider, first, the processes most often used. Different people put their point of view. A decision is then made to accept one or other of the views offered.
Debate is the typical process for exchanging information.
Decisions are most often taken by an arbitrator or leader or by majority vote. To oversimplify the issue somewhat, one of the expressed views prevails. It is commonly found in many of our institutions, such as courts of law, or in politics. In case you were wondering, I don't recommend it. In distinction to this, consensus does not pit one view against another.