The fundamental problem with these systems is Goedelian. Kurt Goedel showed that formal systems like this are unable to extract themselves from these systems.
One problem it has consistently displayed, and which shows that it lacks understanding, is its difficulty dealing with self-reference.
Of course, the dog is responding to words as signals, not as components of sentences.
Many of the attacks result from the skeptics’ failure to properly understand Doug Axe’s 2004 article.