Range judgement requires experience especially in a environment with no background objects for reference. And you must remember, for a pilot under normal non-combat conditions, being a mile away from traffic is considered close.
Hub Zemke wrote that the first time he fired his guns in combat, he *thought* he was tailgating the enemy plane. Gun camera footage revealed he opened up at approximately 1,000 yards. So it is entirely possible that when the new pilot thought he was entirely too close to the target, he was at ~200-300 yards.
Besides, you can find examples of some pretty amazing long-range shots from WWII too. I'm talking about nailing crossers in the 400 yard range. With all our practice, it is no surprise some do this consistently.
BTW, if you do a .target command and shoot the thing from auto-level, you will see dispersion, increasing with range. HTC has not equipped us with unrealistic "laser accurate" guns. Well, you know, except that one time it equipped us with lasers...