"Object has target" doesn't work properly, neither with villagers nor with military units. No matter which target you select, the trigger will always fire as soon as the first object has *any* target.
Example: You want an enemy War Elephant to drop dead as soon as your villager attacks him. You select the villager as the object, the elephant as the target... annnnnnd...
... the stupid elephant dies no matter what your villager does. You can go woodchopping, and the elephant drops dead. You can go berry-picking, and the elephant drops dead. Doh. There's the same problem with military units. To use the same example with a soldier: the elephant will drop dead even if your soldier attacks a building in another corner of the map... or if your soldier boards a transport, or garrisons inside a tower.
Annoying bug. I hope it's fixed in the expansion.
Ingo