Same with the Ostwind, the ack guns, as you mentioned bombers and pintle guns... You can empty the guns of any fighter or bomber in one long burst, when in reality you might burn the barrels up by doing so. The tank main guns also fire at the same rate, switch between ammo types instantly (without reloading), and there is no additional delay if the number of rounds which could be stored in the turret are expended.
So, even where we've got a realistic limitation, we've only got enough to keep gameplay somewhat reined in, and that's good enough. We don't have gun crews, or the amount of antiaircraft fire that would have been available, and we probably have more targets at any one moment, so I personally think they've struck a good compromise in this regard.