Halfway through my career, being on both sides of the table (interviewer and interviewee,) I've observed that a common interviewer mistake is to expect candidates to regurgitate facts; or be able to provide a memorized answer.
In this case, the goal is to hire great engineers; and great engineers do not memorize solutions to every problem, nor can they come up intuitively with great solutions in a matter of minutes.
Their goal is to find a "good fit", not to find a good engineer. That's why their software is so incredibly disfunctional: it's just a reflection of their workplace culture.
In this case, the goal is to hire great engineers; and great engineers do not memorize solutions to every problem, nor can they come up intuitively with great solutions in a matter of minutes.