While point defense is definitely *somewhat* better, it still tracks projectiles after they've been shot down or hit things. To demonstrate, I'm attaching a screenshot of me testing a Smartcannon based PD system for SM&M++.

A drake above me has fired a KM100, which was engaged by my SmartShield. The explosion to my right is where the first round or so connected and destroyed the missile. Note that the other missiles have not lost lock: they're still detecting that there's something to be tracked towards....specifically,they're heading for where the missile *would be* at that time. They should instead lose lock (although I'm about to file a related ticket for something similar). This could be an issue when defending a target (they'll plow straight into whatever the missile was trying to hit if it isn't the player).