Casualty system in A&A is part of the success of the game.
Simple enough for not being too much time consuming but at same time allows for cannon fodder and protection of the expensive units.
If we condsider the real battle attacker do not “know” who are they firing. WW2 was not fought with Napoleonic style battles where 2 armies lined up one in the face of the other.
In WW2 units are camouflaged, entrenched and hidden. When and if a unit is discovered by the enemy it can be target of fire, but attacker is not “selecting” the target among all the defending unit, only the one that has become visible.
So to some extent is the defender, positioning an moving its units, that allow the attacker to fire.
The more “correct” way of picking casualties is the one used in Battle of the Bulge, random selection, with the possibility of overkilling one unit and totally missing another.
If we can not have random casualties then we should stay with the “defender pick the unit to be removed” mechanism.
I am Moses Obama and I endorse this message.
I think that in Anniversary it is the right system. House rule or other ruleset may use different casualties removal system but it is the right thing for the “standard” game.