From one side, we call ourselves problem solvers, on the other hand we are not satisfied with simple solutions to these problems. If im interviewing for a job, i should be expected to behave and solve hypothetical problems the way id do it on the job. If that screws up your script, you probably suck at hiring and communicating your expectations.
In my experience, it's much easier to train somebody on how to scale a basic system up in response to need than it is to get somebody who favors complexity to cut it back.
If anything, it's neurodivergent interviewers. If I insisted on a different design I'd either ask a question that's not solved by "just use postgres" or follow up with "ok, that would work, but what if <something that would prevent postgres from working>". Just failing a candidate for a correct answer is a prime example of why interviewing is so bad.