Over here, the answer (standard interpretation of the guidelines) to your question is simple (sTeamTraen already pointed that way):
There already is a simple way to distinguish those types of caches: the cache type.
If the cache type is "Multicache", the cache has to be solvable in the field. If it's not solvable in the field with basic school knowledge, it's to be classified as "Mystery/Puzzle".
BalkanSabranje