Rank of the third form

Authority, Ranks and Composite Forms of Ijma

ثم إجماع من بعدهم بمنزلة المشهور من الأخبار.
Later consensus is compared to a mashhur report.

The analogy signals an authoritative position, yet one ranked differently from the first two forms. Not every form of agreement carries identical epistemic strength.

Here mashhur is not simply a topic that many people know about; it refers to a recognized category used in the theory of transmitted evidence.