There are two groups that I would argue should be labeled "modern slavery victims"/"slaves". These are the illegal human trafficking victims and the legally (referring to national, not international, law) incarcerated work force.
Off the top of my head, the latter includes the inmates of the American prison industrial complex and the Uighur prisoners in China.
The applicability of the term "modern slaves" to these groups, and the clear difference in the extent of exploitation, between these groups and the Amazon workers, convinces me we must not apply the term "slavery" to the latters' employment.
