TB12 feels most comfortable when he knows in his own heart that he is prepared for the battle he is facing.
He said at the Salem interview that "that he wanted to be comfortable with what he was saying"
This is the essence of TB12, why he works so hard and studies so much before a game. So when he goes onto the field there is nothing left to chance in his mind. That is when he is comfortable, that is when he feels that he will win the game because he has already won it with his preparation.
The media interview happen when he was not able to prepare, in fact all the information that he was being questioned about was a LIE ( I believe by design) and thus he had no explanation. Being a totally honest person, TB12, when asked the question "are you a cheater" Tom had to answer " I do not believe so" for in that totally dishonest circumstance it was the only honest answer he could give. For there was no HONEST explanation for the supposed facts of the situation at that time.