Its not the bolt, its the screen in the bolt. You are right, half leave it out, half put a new one in, and yes leaving it out will let any debris and metal into the turbo that the screen would have caught. The debate is if the screen is clean what would have gotten into the turbo anyways. But if you leave it in, and somthing gets trapped in it, it could choke the oil flow to the turbo. On the other hand if you take it out, and somthing large gets into the turbo cause the screen is gone, it could take out the turbo anyways.
Hope that helps...