The only thing that makes sense in this situation is that you did not answer his phone. If you had actually answered it, your behavior would be more a sign of weirdness than confidence or aggressiveness. This interviewer is screening out applicants on the basis of an unvalidated, unreliable, and simplistic exercise.
Although his objective was to somehow learn about your personality as a result of this so-called test, the only personality traits that can be gleaned from this childish game relate to those of the interviewer himself.
If he is truly interested in learning about your confidence and aggressiveness, the best approach is to base his interview on your work history and include some work sample questions and simulations. That is a far cry from hiding in the next room and waiting to see if you pick up his phone.
Beyond the interview, you have to wonder what kind of manager this individual must be. There is also a question about the kind of people who pass his test and join the company.
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