When I answer the ’phone, I generally say either “Yes?” or “Good day/evening, Sherwoods” rather than “Hello.” With cold-callers I often don’t get a response to that; I pause and try a variation or two of “Is someone there?” before the caller speaks up with a bewildered “Hello?”.
Does their robo-dialer wait for a “Hello” before prompting the human that it has found a live line?