Enemy Ace debuted two decades after WWII. That's not exactly a short period. Heck, the film adaptation of All Quiet on the Western Front, about German soldiers in World War One, won an Academy Award for Best Picture in 1930, only a little over ten years after the war.
Given that, I wouldn't consider Enemy Ace, published forty-five years after the war its about and twenty years after World War II, to be especially daring.