Well we never see a tiny piece of Kryptonite near Superman in the movies. You have to leave the comics out of it. None of these comic book movies ever hold true to the comic story lines. What we do see however is that Superman struggled to get that rock mass off the Earth. We also see him tumble to the Earth because of that tiny shard being inside of him. So....I think you're making a big deal out of nothing. And Brandon Routh was a pretty good clone of Christopher Reeve.