The Four Great References (AN 4.180)

This question refers to The Four Great References in Mahāpadesa Sutta (AN 4.180) . In each case, it ends with: > If they’re not included in the discourses and not found in the texts on > monastic training, you should draw the conclusion: ‘Clearly this is > not the word of the Blessed One, the perfected one, the fully awakened > Buddha. It has been incorrectly memorized by ... > > If they are included in the discourses and found in the texts on > monastic training, you should draw the conclusion: ‘Clearly this is > the word of the Blessed One, the perfected one, the fully awakened > Buddha. It has been correctly memorized by ... So, why are there four great references and not one, if the criteria is the same for each of them? What is the difference between the four great references? Do they represent primacy or order of reliability? For e.g. is the first great reference more reliable than the second great reference?, is the second more reliable than the third? etc. If the answer to the previous question is Yes, then does this imply that the traditional commentaries to the suttas by the Sangha is more reliable than the interpretation of a single monk, as suggested by this comment ?