So other than the progeny part, how is prison labor not exactly what you said? People are literally captured, and based on overturned convictions at least some percentage are innocent. These people are then forced to work and can have their sentence extended arbitrarily by bureaucrats and not the court system. Based on the California example the system even tries to keep people working when given a court order to release people. The only thing preventing the in perpetuity part is basically the good graces of the bureacracy.
I do agree about the overuse of the term in other situations however
You're confusing things. There is a difference between forced hard labor as just (and thus commensurate) punishment for a crime and actual, particular abuses committed by the justice system. There is nothing wrong with forced hard labor as a punishment for a crime to the degree required by justice (and frankly, many crimes deserve far worse). There IS something wrong with inflicting pain on someone who is innocent, esp. when those inflicting the pain do so without authority, without sufficient justification or in excess.
In other words, you think there exist situations in which it is just to enslave people. You're trying to make a distinction that literally no one else makes because you want to separate forced labor as punishment for a crime from the connotations attached to the word slavery. It's just a sleight of hand.
As long as you allow that society has the right to force people to be locked up without their consent because they broke a law, I don't think it's a stretch to say that society has the right to force people to do work.
I don't see why that follows, considering they're two different things. In any case I do think prisons themselves are one of the blights of modern society.
While I'm not certain that society doesn't have the authority to force people to work (though, if it is ambiguous/uncertain, I would advise "don't", and I am not confident it does, so I advise "don't"), but I do agree that it doesn't really seem to follow, at least not without assuming some other premises.
If other entities were not profiting off of the labor I might agree that its a just punishment. However, if they are now cheap labor for companies, and can get extra punishments for not working, that is no longer a punishment in of itself. Its just slavery under the guise of justice
I do agree about the overuse of the term in other situations however