Bills brass does not know anything about that. They do however know first hand the type of player and person Stevie is. The Bills felt it was best to move on. Better for the Bills and Stevie.
Now i do not want to say Stevie is a bad person, i do however think you can not have a guy be a leader who is anti-clutch. Stevie wanted to talk and be a leader, but it just did not translate into game deciding moments on the field. It is a shame, maybe it will change for him in SF.