I recently raised this pet, and for some reason, the form I got was because of 'high affinity to heart'.
This pet has no affinity to heart whatsoever

That little bit of static at the end of this pet's affinity meter probably has some heart. Lump-style animals can be unpredictable and I might want to raise the threshold required for elementalizing them so that trace affinities don't end up determining their form.