Skeleton trap lightning doesn't charge creepers, transform pigs or villagers

This might not be a bug, but it would still be a really awesome feature.

Basically, when you have a skeleton horse with {SkeletonTrap:1b} and let the trap trigger near a creeper, pig or villager, only the other skeleton horses will spawn, while any other mobs aren't affected by the summoned lightning.

Reproduce:
/summon Creeper
/summon EntityHorse ~ ~ ~ {SkeletonTrap:1b}