I may not be the expert on this, but it seems the newer word makes Slavery less of their personality trait, but more than anything it describes an inhumane work condition/living situation that the person is being forced to endure rather than just noting that the person had no autonomy and that they are a “slave” rather than a person with real thoughts and autonomy that are being forced to think another way. It may be semantics but I feel that it makes enough of a difference in what is being said by both words/phrases