The tone of CoC, and the excruciating care with which RF explains his sources and the nature of his information ... in particular, noting what information was hearsay and how he got it ... has the ring of truth. More specifically, it's the style of someone being very careful not to overstate or misstate anything.
RF knows the propaganda value that catching him in a genuine falsehood would have. He seems to have been excruciatingly careful in his writing. And it seems to have paid off. Whatever else RF is criticized for by the WTS, I've never seen him called on a factual error.