Hopefully, the first part where the human<>human chat happens, the candidate is able to see that the intent is to have a genuine conversation, albeit with a more senior person (aka older) person on the other side.
Where I differ from you is the zero-payoff framing. There have been cases where the candidate put me in my place, rightfully so, and ended up getting hired.
This is subjective territory, but I actually prefer a candidate that spars. It gives me a chance to explain my position as well as hear his/hers.