Pit bulls are an easy study in canine muscles. You can see them pretty easily.
Hit a tendon, and that muscle group is down for the count. The dog has a lot more tendons in the chest than humans, and they criss-cross and anchor in areas that are exposed. I’m not talking about “shooting legs off”.
You know more about it than I do, so I will take your word for it. If you can disable a viscous animal at close range that is charging toward you by hitting the tendons then my hat is off to you. All that I would be capable of is hopefully making a few holes in it while aiming at the center of mass. Despite being confronted by many during my lifetime I have never had to shoot a dog.