I'm curious about what context would require an untyped language
By untyped I assume you mean dynamic languages? I’m some contexts it’s not convenient to lug around a type checker, embedded languages for example. Other times if doing macro heavy programming (lisp, forth) it’s hard to build a type system that can properly type check the code or resolve the implicit types in a reasonable amount of time.
In the context of JSON you can work on it without types from a typed language. It’s just that as a force of habit coders may chose to spend time adding types to things when they shouldn’t.
Ok that is very confusing because "dynamic programming" is a very specific thing, and also super popular in leetcode questions. Maybe half the questions on leetcode.com involve dynamic programming.
It has absolutely nothing to do with dynamically typed programming. It's also a really terrible name for what is essentially caching.
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.