Occam sez: It means these two had zilch-nada rôle of responsibility vis-a-vis the anthrax letters in year '01. The US govt would never have freed them, had they been a guiding force. Never.
Why? Above all, the moral hazard, the lesson to others.
If a trial would have revealed too much as some have propposed, then the US would have held them indefinitely or they would have desappeared.
Occam is correct. If either of these 2 even had a tiny connection with the 2001 anthrax attacks, even if they knew recipes similar to the one used in preparing the stuff, the US government would have locked them up and thrown away the key. I'm afraid it is the behavior of a zealot to try and reason otherwise.
We must look elsewhere to find those responsible.