So, sentient means 'having the ability to learn new things' ? Kinda like humans, who are born with certain instincts, but are then able to learn new things or 're-program' themselves.

Well, there is a filed called 'machine learning', which helps design robots who will be able to learn. If they are able to learn and exhibit intelligent behavior, then we have to treat them as something more than rocks or hammers.

That is what the document is referring to - not pre-programmed robots, but AIs (robots who are able to learn, perceive, change behavior etc.).