There are hundreds if not thousands of prisoners being kept out of Gen pop, who do not confess murder to the warden, several guards and prisoners and their families, 61 x.
I have my doubts about the DT's description of his 'torture.' He did have people to talk to, obviously. And he had his own tablet until he himself destroyed it. It wasn't true that he was tortured by darkness or lights on 24/7 because he had his own light switch. And he did have exercise time.
I think the confessions came about because he was alone with his thoughts in his cell, and the guilt must have been overwhelming. IMO