I'll answer, since Susie hasn't actually processed any rabbits
I don't wait around for runts to get to market size, they get processed with with the rest of the litter on time. Usually, they catch up and I don't even know who the runt was.
Sometimes they are a lb. light, say 4 lbs. when the rest are 5.
I grind a lot of rabbit meat, so I'm not very useful for describing texture.
But, since I raise rabbits for pet food as well as human food, some smaller or tougher kits are no problem for me.
They don't seem to eat quite as much as faster growing kits, but,
I have absolutely no numbers to back that up. So it should be viewed as an opinion statement rather than a fact.
Any and all kits with noticeable GI problems get euthanized, since I've determined that rabbits with gi problems suffer quite a bit.
Most of the time, I never see anything wrong inside at butchering time.
But, when I do find an anomaly it's usually in the intestines.
I have never seen a malformed rabbit heart, but a close friend has. (She unfortunately didn't get a pic.)