It sounds like someone had a pup bite a person with a mental problem in the family, and had other pups that developed some problems like cancer, digestive problems, or hip/elbow problems.
All breeders sooner or later will produce some serious health, structural, or even temperament problems. It sounds like this breeder will, most likely, blame the owners for their method of care, and unless you have receipts that PROVE the dog is eating the diet that they want the dog to eat, and prove that you have not allowed the dog to pull (how?) their health warranty isn't worth the parchment it is typed on.
I would pass.
Breeders should educate and encourage buyers to raise and train the puppy in the way that is successful in their lines, but to demand it, and to void a warranty due to a list of ordinary environmental things, is over the top.
Requiring a diagnosis, or second opinion with a specialist, certain tests or certifying agencies for some conditions, is reasonable.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC