Thanks for bringing up that program site (link, for convenience)

Like you said, it's hard to know the internal situation in the prison, so it's reasonable to want to avoid labeling this specific case as slavery or not without further evidence. The title is ultimately subjective, rather than the objective titles a news community typically encourages (by 'subjective', I'm referring to the fact that different worldviews have different interpretations of slavery, even up to the point where many through history consider regular work to be wage slavery based on a holistic analysis of labor in society)