I'm a little confused by this use of the word sentient. I understand it to mean "qualia-bearing", and I believe that chimps and other animals probably have qualia. Perhaps they meant that it probably didn't have our depth of human experience, i.e. it probably had a similar degree of consciousness (or qualia) to a chimp.

I suspect that it's simply down to sentient vs. sapient being one of the most common word confusions in the English language.