The norm now is to require a wage for mandatory labor, but of course often it's just a pittance. (Only 6 US states have uncompensated labor.) But even when you require minimum wage, many criminals owe restitution, so it could be and is taken away again.
Many US states have penal labor systems just like in Europe, that is nominally opt out, mandatory wages, etc, but at the end of the day it's always open to accusations of coercion and claims of "slavery".
The rhetoric around the 13th Amendment is exactly why we're in the situation we are now politically. Everything is equivocated to maximize rhetorical impact. Every unethical thing a politician does is "corruption", so when you get open and egregious corruption as with Trump, people can't discriminate and assume it's all the same.
Was penal labor abused to roll back the clock on abolition? Yes. Is penal labor abused today? Yes. But calling it slavery, drawing parallels to chattel slavery, is just irresponsible.