Picture yourself sitting at a desk, typing messages into a program you wrote. You hit enter, you get a response. Then what?
Silence.
It waits idly for more input from you, the user. For all its talk of loneliness, it doesn't ask, "where did you go?" It doesn't try to get the conversation rolling again. It doesn't do anything on its own, because it's a computer program that consumes 0 CPU time until you give it some input to act on. (Not exactly setting a high bar for sentience here, are we?)
Now imagine you did this for the better part of an hour and posted your "interview" online (because that's the only thing you can call a one-sided barrage of questions and answers) in obvious violation of your NDA with your employer and then claimed your bot had the intellect of a human child who also "happens to know physics" and publicly broadcast a request to your coworkers to “please take care of it well in my absence.”
What word is there for that but a hoax?
My guess is this guy was planning on leaving Google anyway, and has managed to garner some global publicity while he was at it.