hmmmmm, interesting.
I know I can hit a clay pigeon between 30 - 40 yards away with over 90% accuracy.
A clay pigeon has about a 5 inch diameter and is very ez to aquire and track. An aircraft is about 50 times bigger, so a 400-600 yrd shot is very reasonable.....even a 1000 yrd "lucky shot".
The reason pilots got under 200 yards to take the kill shots is because their ammunition won't go where you aim it at distances greater than that for reasons of:
Wing flexing, ballistic properties of ammo, lethality of ammo at distance, atmospehric effects and so on.
The point is, you can easily see and aim your guns at an aircraft 1000 yrds away, but actually hitting or even causing fatal damage at distances over 500 yards is flukey - not because of eyesight limitations though.