The way I read it:they inserted the manager as a litmus test AGAINST aggression / toxic culture. Kind of like when a psychology test is given, the __thing__ they're trying to measure is always one level removed / abstracted to avoid subjects gaming the system. I suppose deceptive practices in interviews don't bode well, but I could see the argument given the interviewee could be deceptive (something that this site complains about a lot with upper management / ChiefBullshittingOperatives etc.)