That is false, it targets the player it perceives as the biggest threat in its lock on area.

I just joined a game, so I was 0-0 with 0 points and last place on my team. Immediately heard "Enemy Hind incoming" so I stayed whereI spawned and took out my stinger. I started to lock onto the Heli as it entered the map, and the second it got onto the map it shot at me and killed me just as I fired the stinger. It targeted me because I was the biggest threat at that time considering I was locking onto it.

So your theory is sort of correct, it goes for the biggest threat in its line of sight. That isn't always the highest scoring player, but it can be.

But thats how its been since MW2. It always goes for the top scoring player but will also kill someone else on its way to find him.

I never heard of the heli going for specific targets. I always thought it was random. If that's the case I should be the biggest target for a heli because my goal(and I usually accomplish it)is to shoot down a heli before it reaches the map.