Why? Because there was no fraud involved, and if Xavier had lost the animal, from his breeding, feeding, etc, it would have been on him and we wouldn't be here. However, the buyer was aware of these issues, youth, breeding, etc (that you just pointed out) and assumed responsibility when he purchased the animal.
The fact of the matter (IMO) is that when dealing with live entities there is no guarantee. The buyer can not be held responsible for selling an OUTWARDLY healthy animal unless PRIOR illness can be proven.
Personally, I would not spend that kind of money on an animal that was bred before being shipped to me. I am also leery about buying grown animals, because there's really no way to know how many times the animal has been bred, whether there were ever any complications and how old the animal actually is. Personally, I prefer to raise my own hatchlings to prevent these kinds of outcomes where possible. Purchasing hatchlings gives the buyer time, and opportunity for de-stressing, observing the health, and quarantining the animal.
We are not keeping the parties from working out anything, but the buyer really screwed his case by:
1. Being caught in untruths, fabrications, exaggerations
2. Not quarantining
3. Not having possession of the animal
Thus unless the report proves a pre-existing condition, he's out of luck.
I don't think it can be any more simple than that.
BTW: I was going to leave the "Power-feeding" implication alone, but wanted to mention that it's not unusual for a yearling to reach those weights without power-feeding.