Why do you confuse "rehabilitation" with "acting"?
If a patient goes to a doctor and their wound heals, is that "acting healthy"?
You can make a case that we can't know if someone is rehabilitated, but if you think rehabilitation can be a thing, that necessarily includes being able to distinguish acting from genuine change.
I don't believe you can distinguish the two, especially when someone takes a deliberate and motivated action which they can fully expect to land them in prison. (See: organized crime.)
If a patient goes to a doctor and their wound heals, is that "acting healthy"?
You can make a case that we can't know if someone is rehabilitated, but if you think rehabilitation can be a thing, that necessarily includes being able to distinguish acting from genuine change.