From the way it is described the basic premise doesn’t seem to change. Is it reasonable to imagine slaves were treated better or had any more rights than African Slaves were in the US, I must say i don’t think it is a reasonable assumption. I also don’t think it is as relevant as the fact that Exodus 21 is describing laws claimed to come from a deity, a deity who is also claimed to have finally decided a personal appearance was called for in Palestine 2 millennia ago, who when asked emphatically and unambiguously endorsed the entirety of those laws, even the ones that are contradicted by some stuff he is alleged to have said by the anonymous hearsay of the gospels.