Sometimes going off script is OK but that is not what they wanted here, it seems. Besides I guess that if this interview ever happened, the "solution" might not

Sometimes going off script is OK but that is not what they wanted here, it seems. Besides I guess that if this interview ever happened, the "solution" might not be the reason that they weren't hired. But the numerous hints that the candidate got suggest that they wanted a normal solution. Asking someone to deliver a solution within some reasonable constraints is not "joyless" and disregarding these constraints on purpose over and over is not "smart."