Yeah, incidental contact happens. But it's generally when both players are hunkering down for an impact. Not when one is running along (stupidly unaware, yes, but that's not the point here) and the other levels him. If you do that, as in hit a player that's just running along, you'd best be sure your helmet is not slamming into the other guy's at the same time your shoulder is hitting his chest. They will call that as targeting a player above the shoulders. It doesn't have to be intentional - it's a circumstance where a high hit is made that didn't need to be so high as to initiate contact with the helmet, and they will flag it if they see it.