Some surveys have mandatory multiple choice answers with a NONE option as the exclusive non-answer. This ensures that there is an actual answer given (rather than having the user simply avoid checking any boxes).

Say you have a survey that asks which months are the best and worst for a symptom, and you want to use array_filter_exclude for the worst months (so that you can't say that your best and worst months were the same). Both lists need the "NONE" exclusive option. However, those NONE values should not be array_filter_excluded (e.g. just because you have no best months doesn't mean you have no worst months).

So, need array_filter_exclude to gracefully handle situations where the author has mismatched lists of sub-questions.