Preach, some of the old jaw traps would break bones as they were made to close tightly together and it was that inital smash of the heavey springs and tight fitting jaws that did it. This was true mostly when large traps caught smaller animals eg. #4 Dbl long spring on a fox or coon. I know for sure on the coons, and one broken finger
I had an old trap that I used on beaver and it was like 2 sizes bigger than a #4 Victor dbl long spring, even though the springs were weak those jaws came together with one heck of a smash. Lost that trap a few seasons back due to some ice on the river that took it.
It would only be a wall hanger now as the jaw spread was around 9" or 10" and the most we are aloud is 7.5". But yes you are right most of the damage is done by the animal strugling to free it's self. This is less likely to happen with the os and laminated jaw traps of today.