They come from James Lamb's Free book Training Your Retriever. The book itself has been in print since 1949 and the standard writen was AKC standard in 1957 well before the Lab became popular. It's the only standard I've used for picking the 4 Labs I've had over the years. His book make some interesting observations. While alot of people dismiss Free I've found his common sense and wisdom invaluable over the last 30+ years when it came to picking and training my dogs.
Intresting to note that one never really heard of elbow trouble in Labs or dogs that "shouldn't be allowed to jump down out of a pickup" years back.
It's mentioned in the book about the breed's excellent nose , a trait overlooked in the bigger is better crowd.