Instead of approaching it from a perfect orientation you are privileged to 70 years later. The friendly fire problems were at the very beginning of the Pacific war before anyone was forced to toss their pre-war assumptions and take a real look at the mistakes real people were making due to them. Early war crews trained by pre-war procedures. BoB and rifle caliber machine guns harmonized 400-600 comes to mind. Early NAVY aviation experts believed the Pacific air war would only matter by shooting down bombers. So fighter harmonization patterns were focused at 600yds and as scattered as possible to chew up bombers. Even as late as the first Jug missions into the ETO, allied gunners shot at them thinking they were 190s.
We know from today that individuals without specific training fail shooter tests under the stress of the test. If both a zero and a wildcat have a radial engine, the gunners only know it sounds radial. Markings don't come into play at max range for defense cannons, most planes in motion at a distance look one color. Did all gun positions in fleets early on have a dedicated spotter glassing the incoming for identification? Or was that simple addition to each battery a result of human nature running over pre-war assumptions about men in combat?
