Not to defend the theater aspect, but my (rather limited) understanding of effective security interview involves a series of questions and evaluation of performance across the responses. A single question by itself may not have much inherent meaning, but the composite can be quite effective.
Can be. Not saying that's what they are doing in this instance.
"... effective security interview involves a series of questions and evaluation of performance across the responses ..."
True.
Add demeanor, body language, appearance to these questions. I think there a lot of non-verbal questions being asked by the person looking at visitors. One of the most useful is the ability to read"body language" and fit. Does this person fit the right pattern? Are they hiding something documentation and other procedures missed? Of course this will get a lot of false positives like the parent post.
Pretty standard questions to check to see if you are really doing what you say you are doing. Visiting? Business or holiday? Where are you staying? Got enough cash to cover that stay? The best thing to do is pre-book, take a print-out of where you are staying on your itinerary. Just doing their job - looking for travelers not sticking to their plan.