Ah, that makes sense! Didn't see the chocolate, but 'mallows burnt to crisp become much lighter in such a "sandwich". We hypothesize it's the unburnt inside part showing through, why not...
Attempts to fry some bread or light up a wet log pile proved unsuccessful, but the ability to blow out flaming food was fun. Though tossing burning food _into_ the fire would make more fire safety sense than tossing it "somewhere" (yeah, some people hoped for a larger fire and seeing the marshmallow become extra-bright, if short-lived, fuel, like newspaper and paper tissues do).
Oh, and, as people who've tried starting a fire from a match, everybody I know tried to use newspaper as kindling before lighting a match!