I think you might have missed the full implication of that part.

Certainly, a sentient being can learn new things, but that's a matter of rule-base and memory. No actual intelligence required, IMO. Sentience, to me, goes toward a concept of self. Of being aware that one exists and is responsible for one's own actions.

Personally, I fine with having really smart-but-not-sentient hammers. I'd rather not have to lard up machinery with some touchy-feely "it's alive" sentiment. We won't have to have lots of hand-waving over whether or not that hammer is a slave or not.

If we can have an army of dumb robots performing the work that slaves do now more efficiently and cheaply, then we can easily spot the slave owners and remove them.