Very interesting point!
Though the wording in 1942, 2nd Edition, is different:
@rulebook:
No Combat Value: It can, however, be taken as a casualty. If a territory containing AAA units and no combat units is attacked,
the AAA units are automatically destroyed. AAA units may never attack.
Air Defense: An Antiaircraft artillery (AAA) unit can fire only at an air unit when that unit attacks the territory containing
that AAA unit. AAA units fire only once, before the first round of combat.
This would indicate that the air unit is subject to AAA fire, and after that - if the air unit survives - the AAA will be autodestroyed.
As the combat value of an AAA unit is relevant only after the AAA fire itself.
Also see page 12:
@the:
Air units attacking territories that have antiaircraft artillery will be fired upon (see pg. 25).
So I think in this game it works like expected again.