I think you are right, I also looked into this blood years ago to acquire some for the Clouse & Bolio to add with some other strains I was using. While it was costly I learned that the biggest reason most have this blood was to say that they have it. Spoke with a gentleman who used it from California, he stated for competing reasons the blood was nothing more than a filler, he said in order to compete with it you would without doubt have to cross it. Then went to unlock some secrets and says yes it's known for it's gameness but some of the dogs being toted as Premier studs were of lesser quality and were opposite of what the line is known for. He said it does add a good element of air and breaks down the body frame of blood.
Some fellas who liked Boyles bred type dogs or Eli family dogs sometimes get barrel chested or just bulky and come in as the smaller dog on weight or have to go up in weight because the weight loss is too much. He said the KZB blood would help that and put some good air into them. Opposite of Mr VIP (please remember this is just one group of guys opinion) they weren't durable. Said most of the game ones weren't durable at all that's why you hear about the gameness but never much proof because they show a lot of heart in school and around but typically weren't durable enough after school to go get ribbons.