I think that the strength of relevant muscles is probably important to some degree but I don't really think that size = relevant strength when it comes to those muscles. It's not like you need beefy forearms to support the elbow. To strengthen those muscles you'd be doing like, grip strength stuff and little bitty wrist curls.
Sale could be a twig and still have 80 grade flexor muscles. But there really isn't any special reason why Chris Sale stays healthy, I think he just illustrates the general point that all of this s*** works in the range of probabilities and nothing is certain. Pack-a-day smoker can live until 90!