The real kills for most air-to-air claims are about 1/3 to 1/2 of the number claimed.
The reason is not dishonesty, but combat. If two B-17 gunners were shooting at the same aircraft and it caught fire and went down, both probably thought THEY had killed it, and claimed it that way. If the fire later went out and the palne glided or landed safely and was subsequently repaired, then we claimed two that resulted in a real loss of zero.
Much the same can be said of fighter-versus-fighter combat in many situations, and a sudden burst of fire doesn't always mean a kill.
Happened in ALL WWII air forces, but happens much more infrequently today since most missions are flown with MANY fewer aircraft and, MUCH better weapons, and modern radar confirmation of the real losses.
As for bomber gunners, they thought EVERYTHING was hostile. The educated bomber gunner who could recognize a P-47 from an FW 190 was something of a minor rarity.