True, but based on my experience with Jersey giants it's just deceiving. Yes they grow their frame first then put on weight, but I'll bet they still have as much meat or more as any other heritage breed chicken. Its just that the body is so big you'd think they would weigh more, chicken bones don't weigh much. I've processed quite a few young birds and was never disappointed. I process all as soon as they start crowing and the giants have weighed as much as or more than the other breeds, though you can not fit them in a gallon freezer bag, and the other breeds fit. I think it's just deceiving thinking they should weigh more cause they are bigger.
Nine month cockerels resemble turkey legs and as far as the breast goes not plump and thick like a CX but they make it up in the length, and excellent meat. I would put money on they have just as much if not more meat then a CX (but of course CX are only weeks old)
Some people say they eat like hogs also, I don't think so. Mine don't eat much. They're not super active hyper birds, pretty docile and calm. Even in winter they don't eat any more than other breeds I've had.
They lay great also, and I've had them lay all winter with no supplemental light. IMHO they make great dual purpose.