With the cache scanning enabled, you'll get notices before you even can see the mob. The macro, from my inderstanding, will just target any nearby that it finds. It's probably going to be more useful without the cache scanning on, since once you see it and get the notification window pop-up, you can then click that pop-up window to target the mob.
and it would then work for the nameplate scanning..?
Granted, I'm a Lua noob, so I'm not sure if it's that simple or would require something else. :p
Edit: Well, I guess (if I'm following correctly) that there would need to be more to it, as I'm guessing that wouldn't handle toggling nameplates mid-game... But in any event, to me that looks like the CVar that it would need to leverage.
Yeah... Seems to still track when it sees the rare mobs (as time in the tooltip updates), but I get no chat message or Parrot output any longer when one's spotted. Would be nice if it could be updated. :)