I absolutely believe that I could readily smash someone’s shin who has been training iron shin. It does not make you impervious. Shin conditioning (which is all iron shin is) can thicken the shin bone through repeated hammering, which causes additional bone growth and toughens the bone. It can also reduce the perception of pain by damaging the nerves, which might be practical in the short run, but is a bad thing in the long run. Seriously, you want to keep your nerves. Life is more pleasant when you can feel things, and the perception of pain warns you when you are injured and might need life-saving medical treatment. The perception of pain is a very important life-saving trait. Shin conditioning therefor can make the shin less susceptible to breaking and can make it somewhat easier for someone to shrug off a hit to the shin. But I assure you, I could still smash a shin with my sticks. He is gonna feel it, and it will destroy his support platform making it impossible for him to stand. Shin conditioning can make the shins tougher, but it is not a magic spell.