I highly doubt your pedigree for commenting on the history of criminal justice research.
So a court ordered sentence backed up with the threat of prison time for violating any of the terms is equivalent to voluntarily checking yourself into rehab. I'm sorry I need to point this out to anyone else reading this and banging their heads off their desks, but in one instance offenders must exactly follow the terms of their sentence under penalty of the law, and the other is purely voluntary and lacks any legal obligations whatsoever.
Shocker upon shockers, those are not the same.
All sentences given out to criminal offenders are necessarily punishments whether they, at one end of the spectrum, receive probation or, at the other, the death penalty. Any kind of sentence involves some involuntary loss of freedom whether it involves adhering to special probation terms (which usually require abstaining from consuming alcohol or similar restrictions of ordinary civic rights), performing community service, paying fines and restitution, submitting to a court-ordered treatment plan, various lengths and types of confinement through imprisonment, and so on. Again, the criminal justice system employs many more forms of punishment than imprisonment.