Its just a matter of the bolts being stronger because of the material they are made of. Galvanized bolts will resist corrosion and will last longer. I don't think I've seen a broken bolt that wasn't corroded in one way or another that was in the steering box (yeah, i've broken brand new bolts before, that's not what I'm saying). So the idea is not just to get stronger bolts, but to protect them from corrosion.