There are exceptions to this. There was a full blown dialogue leak for Chapter 984 or 985 that came out before any summary or image. People even called it fake until pics came out. Only then was it verified. There were a few other instances were 5ch spoilers have been legit without Redon confirming.
Anyway, yes. Redon really is the foolproof source. At worst, only follow his posts outside of pics if you want whats true.