I stand by my point that at 5 yards, you are going to be focusing at the threat; you aren't going to have time to be looking at your sights.
I don't agree that you won't have time, because like I said it really takes no time at all. I tested that for my self, and found time not to be an issue when shooting with the FS. For others, you may be correct, but I think that with much practice, they would become just as fast focusing on the FS as they are when shooting without the sights.
When talking about a gunfight and not just a shooting exercise, I do FULLY agree with you that you or I probably would not look at our sights in a fight at these distances. Thank God I've never been in a real life or death gunfight, but from my experience with force on force I found what you said to be true. When I had to shoot a threat(s) in FOF, I would notice my sights only in my peripheral vision when shooting iso, but my primary focus was on the threat. This is a big reason why I found CAR to work so well for me. Firing the weapon (pistol in this case) in the CAR extended position, places the front sight right in my natural focal point. The natural focal point is the distance you would hold a newspaper away from your eyes to read it. Its the distance in which you feel most comfortable focusing on something with your eyes. When I fire my gun in this fashion, I still focus on the threat because my natrual response is to get completely fixated on the threat, specifically the threat's weapon. Even though I am focusing on the theat, I can still very clearly see one front sight superimposed over my target because the front sight is held at my natural focal point.