The second thing is that there's no way to measure pain, and also what we feel as pain is more like two things, actual pain, as in nervous system reaction, and suffering, which you create in your mind. There's two-way causation between the two by default, but the effect of one on the other is not deterministic, and can be learnt to that you feel pain, but do not suffer (as much you did previously). So we couldn't measure the pain before, and now we cannot measure the suffering to an even lesser degree.

The third thing is, which usually comes up with regards to crime, is punishment vs rehabilitation. What you describe with the AI, as it stands, is punishment. It's up the person being punished to learn something there. I don't have high expectation of someone who's returned to society after such lengthy torture (or are we killing them afterwards, or keeping them otherwise captive?). In case you're a victim of a crime, or just someone affected, it's natural to thirst punishment for the perpetrator. On a societal level however, it seems like that we're better off with rehabilitation. It creates a better social environment for all.

https://www.uib.no/en/news/100126/norwegian-prisons-rehabili...