Yeah but nobody can explain why Marty would tell the detectives that. He just told them "Rust was trying to get a read on you". So....how does that make sense?
its common knowledge that Rust is some sort of interrogation room savant. whether he is doing the interrogating or it appears that he is being interrogated its safe to assume he is in control when in the "box". Marty has referenced his skills in there several times and the 2 2012 detectives even asked Rust about his interrogation skills. What Marty gave them is just common knowledge....