You can yeet goldfish. Carp are stupid tough. It's the tropical fish we often keep that are kinda wimpy. Also, they're not coming from a super healthy environment (the store) to our tanks.
I definitely have not, and now I have. I'm unsure if I should thank you for this or not.
I feel like it takes the sport out of it if the fish is dead though. The whole sport of the carp throwing is that a carp absolutely can kick a grown man's ass and flop to freedom if he isn't careful. You leave a carp alone long enough and those things turn into damn near coelacanths. They'll eat your dog. Manhandling one of those suckers into a parabolic arc is going to take skill, strength, planning, and luck.
One reason is because the hatcheries are in the same general area as the lakes, so conditions are pretty similar. The temperature will be about the same at the same depths as the hatchery, and the water comes from the same source.