I've subscried to the opinon that (wow that sounds like a bullshit phase!) the bar moves in a subtle S-shape on the way up, and a slight U-shape as it comes down. From the chest drive, most of the muscles of the pectorals are fanning from the lower portions, and a strong contraction of the pecs (and lats) will tend to cause the first direction to be slightly towward to the feet. As the triceps and delts accept the changeover of responsibility for the lift, the bar comes back upwards towward the face, before the bar gets locked out above the chest. The S-groove may only be a few inches either way and may ne even be noticable, but it's enough to stop me using a smith machine for bench presses!
The exagerations about rows to the neck, etc were just to prove a point, that when you vary an exerecise it has the potential to either render the exercise less effective, or make it downright dangerous. The point about doing BP to the neck is to "isolate" the pecs, right? The prob with this is that the whole idea of compound lifts is to get the whole chain involved and NOT to isolate muscles. You lift less weight in a totally unnatural (non-functional) way and then have in increase risk of injury for your troubles. It's likely that although you have not had shoulder problems yet, it's probably more due to luck and the fact that the poundages are still within your shoulder's comfort zone.