Some members of CathInfo only post through the intermediary of private communications with Matthew. I refer to these as "super-members".
With all due respect, I am more inclined to accept the honesty of a bishop (and priest of 40+ years), than a young man pressured into gossiping about a rival Resistance seminary.
One could also say that they would rather trust a high priest than a poor carpenter from Galilee. Reception of Holy Orders has little bearing on a man's truthfulness.
It's quite possible that both parties think they are telling the truth; for example, Bishop Faure could have explained in a general way to Mr. de La Chanonie that he would be welcome at the seminary on the condition of keeping his sedevacantism private, with the latter interpreting this as an outright invitation. Hard to know without a lawyerly cross-examination.