It was the whole point of the exercise if I read the article correct
"While the base algorithm is very simple, the point of the exercise is that the interviewer will add new rules to test how you update the code while keeping it readable and maintainable."
Good point. I don't know why that stood out to me so much less than "the interviewer noted that I could even use esoteric programming languages" which to me is code for "go nuts and do stupid fun stuff like writing your whole solution in APL for the extra challenge of it" or other flashy passion-having-shibboleths, which are usually incompatible with readability or maintainability.
"While the base algorithm is very simple, the point of the exercise is that the interviewer will add new rules to test how you update the code while keeping it readable and maintainable."