You can leave. You can get up and walk away and deal with the law, and possibly go to jail. In this case, it'll 'free' them because they are being defrauded according to the author. A slave cannot leave. A slave will not be jailed, a slave will be returned to their master and forced to work again.
I'm not an expert on this subject, but have learned in the past minute of looking at the bonded labor links in this thread that the UN and other international organizations agree that bonded labor is within the modern definition of slavery. Do you have any sources that say otherwise?
The right to choose is only ever as good as your BATNA, it does not confer power in and of itself. Also, are you sure they're aware of their ability to leave without government-enforced intervention?
It's not an issue of whether they are aware or not. By the author's own admission, they are only staying because of their own sense of duty, that the debt is illegal, that they are being defrauded.
It's one thing to say, workers are being shorted, cheated, etc, but if your headline is "your iphone is being built by slaves" then you should be referring to, at least, people who are being held against their will. Not simply people who are confused about the law and are working for free because of this confusion.
So you're saying they are confused about their legal rights? As in, they are threatened with violent arrest, imprisonment, loss of their children, and torturous prison conditions. You don't see the powerful coercion to perform bonded labor here?
Never mind that the slavemongers are generally incredibly abusive on their own because their victims believe they will have no recourse from the government.
Do you understand what debt bondage is? If you walk away from debt bondage in a society that enforces it, you get dragged back to working in debt bondage.
Honestly this is such a pedantic distinction to make for anybody but a human rights lawyer in court.
It's fucked up, but it's not slavery.