I thought this has become standard procedure for high-profile hacker types. It comes down to uneducated LEOs (all over the world) that think hacking/computing is the modern-day equivalent of sorcery or magic, and thus the person of interest has nearly unlimited powers if you let them near a device, another person that has access to a device, or even other inmates that have access to people that have access to devices. I think once Mitnick was put in solitary, it just became the way things are done now.