Like FLS said, it's the opposite side of the coin of an aircraft that is pinged up, but otherwise undamaged, crashing due to pilot error unrelated to the fight and awarding the pining pilot essentially a free kill.
Russians had to go out and find the wreckage, or have the wreckage confirmed by ground troops, of the aircraft they shot down to get credit for a kill.
It's just the "Rules" within the parameters of the "Game".
wrongway