To be clear I wasn't referring 'dynamic programming' but as you say, the use of a dynamic language, or programming without types, mimicking what I assumed the original poster I replied to meant.

My guess is that interviewees wishing to return to the typed world they are comfortable with would first try to type the JSON they are working with. Given that the JSON is messy this could be an unbounded amount of work that is unlikely to pay-off within the span of an interview.