OK, so they're not slaves, they're just people who enjoy no freedom, can be sent to and from facilities at the state's whim, and who are subject to forced labor. I feel like this is a distinction without a difference.
The difference is that you committed a crime, landed yourself in jail, are not the property of the state, and have a finite term to serve. Sounds like a big difference to me.
Explicit slavery as punishment for a crime and/or for a fixed term is not uncommon; clearly the slaves in US prisons aren't fee simple property of the state, but fee simple isn't the only kind of property relationship.
None of the elements you mention distinguish US penal slavery from historical institutions hmthst were unambiguously recognized as slavery.
Historically, that was at times abused by simply creating a lot of laws you could wantonly charge black people with breaking. But even setting that aside, we are simply calling slavery (or, at best, indentured servitude) an appropriate punishment for crime, not describing some phenomenon wholly different in kind.
Consider the text of the Thirteenth Amendment. It specifically exempts prison labor from its prohibition on slavery.
Does not seem any different to me, if the only difference is the jail, you can just create a bullshit law to put those people in jail (see the war on drugs).
