However, the reason these are not comparable is proof of work/investment. Presumably Duplex can or will soon be able to make millions of calls for any purpose whatsoever. Unlike a human being with a foreign accent perhaps or other alerting auditory factors Duplex massively reduces the cost of experimental manipulation.
One of the most successful hacking techniques is phishing. Its success is directly tied to how compelling it is at counterfeiting a legit communication.
And this does not even touch on larger institutional deception.