That’s called an “asymmetrical paunch” or something of the like, I believe. I think it’s a defect.
No organs. It’s just flesh. It won’t harm or unbalance the bird.
A paunch is more for looks than anything. Just a bit of flesh and feathers.
A breed standard will call for one, two, or zero lobes in a paunch in a goose breeds.
Many heavier breeds will have them while some lighter breeds will not.
Much attention is paid to it because it effects the symmetry of...