Why do the zombies take to cannibalism? Humans, mirrored or not, are genetically programmed against cannibalism. Eating human fresh triggers a mental impulse to stop immediately, and this arrests the hunger to feed temporarily. Mirrored beings are not compatible with non-mirrored food. They remain hungry when they feed on non-mirrored food. As their hunger mounts they eventually turn to cannibalism to relief their hunger.
But first breakfast...