What they were looking at was not the code, but the attitude. They likely don't want an engineer with a propensity to do too much, unless it's a 100x coder who can do "too much" with a lightning speed. Usually they want he candidate to show the ability to quickly do as much as needed, and not more, and, crucially, to understand how much is needed.

So yes, this is a culture fit test as much (if not more) as a design and coding test. Some people who are great at design and coding would fail it, and it's how this filter is intended to work.