I'm just talking about land based AAs which will use terrain.

Also I've mentioned MOBILE AA's? Those that can move and deploy anywhere? The enemy won't have an accurate position if they are stationary and then moved to somewhere else. If an area WAS clear, the enemy wouldn't hesitate to chase any airplanes into it. If using mobile AAs and move into clear area in conjecture with the bait and lure tactic, the enemy may not know about the new AAs until too late. There are many similar tactics out there, I'm just listing an example