I think it follows from common sense. LE admitted that the parents were both given poly's at the start. ER said she passed hers.
I believe that MR would have leaked that news as well, IF he had passed.
CR has been publicly calling his father out for not agreeing to take another test. If CR was lying or mistaken, why wouldn't MR CORRECT HIM publicly?
I don't think it is rumor. I believe that MR would correct the rumor if it was false. JMO
It is my impression that MR does not care to insult himself by defending himself to his own son via the media.
That being said, I hope he is attempting to do so privately-- speaking to Cory about Cory's obvious concerns. Though it doesn't sound like this is happening. IF it is, I am of the opinion that anything MR said would be a "lie" etc etc. to Cory like some have said (no matter what he said or how true it was).