Right-clicking an adult mule with spawn egg does not spawn baby mule

Can't reproduce

The ticket title was changed. When I tested it, it only said that mules are affected. And I was able to confirm that.

Confirmed and changed the title back. Mules are the only affected animals.

Zombies are also affected by this, but that's a (needlessly) controversial one.

Zombies are not breedable animals.

Zombie horses, skeleton horses and polar bears are also not breedable animals.

Yeah, zombies eggs should be able to spawn baby zombies but that just my opinion. Anyways I can reproduce this issue.