It is hard to make any confident claims when so much depends on the details. As a very simplistic example, a US-based firm could outsource manual content moderations to a Kenyan for a wage that is low by Kenyan standards (as described in the links you shared), or it could pay a Kenyan an wage that is excellent by Kenyan standards to do a "good" job.

I care about labor rights, and it is no surprise that some US-based companies pay small amounts of money to people in underdeveloped countries for unpleasant tasks. I dislike it, but it doesn't seem very tractable to me. Imagine how incredibly hard it would be for the US government to adopt a law that all outsourcing must comply with US labor law.

There is also the old argument that this job may be terrible, but people choose to do it because it is the best option available to them, it is better than the alternatives. Many young people from rural areas migrate to cities and work very unenjoyable jobs in factories because they find it preferable to staying in the countryside and being a farmer. I'm not fully convinced by this argument, but I do think that there is some aspect of it that makes sense: these people are choosing to do this job rather than other jobs.

It does seem bad if prohibited dangerous models could be trained in other jurisdictions, but the issues there - about regulating developers and datacenters - seem quite distinct from data labeling and the like, which seems to be the sorts of services that are currently outsourced in the way you described.