Indeed if you careful read my message you will see I totally get that you could have an incomplete checker that might work for many answers but it would potentially give lots of false negatives. Ie: fails where a the user actually passed. Your "don't know" state. Since as you say the current design is binary that isn't currently an option as I understand it. Thus the checker would give false results, correct?
I have 35 years programming experience. Writing something to partially check is fine but in the absence of a complete dictionary of answers to check no checker is going to accurately give a list of all possible foods. For example.
Since the user posting the question gave the impression they thought doing a drink one would be easy since a partial food one was done I was attempting to explain the scope of the problem in producing a comprehensive solution.