why doesn't the enemy attack helicopter count as aerial vehicle or lethal aerial scorestreak in black ops?

[Organdonor1900]

On 2 seperate occasions I've recieved the dead bird medal for shooting down attack choppers with a launcher, but the only thing that counts for Sims operator mission is when I down the supply copter? Shouldn't they just word the mission that way instead of wasting time, lives and patience shooting down non-counting items?