The Angry One wrote...
The idol does communicate with it's "hosts". It did with Bartrand, and some NPC chatter implies it did with Meredith too.
Or it could be as simple as the statues drawing power from the sword by proximity alone, and obeying the will of that power source.
It might also explain why Meredith turned into a statue, the statues fed off the sword, the sword fed off Meredith.
On a related note... One of the things I found interesting about the fact that the idol was made of lyrium was the effect it seemed to have on people. Dwarves are noted for being much less affected by lyrium than humans; it comes from the same place their magic resistance does, as well as the fact they don't go to the fade when they dream. Because of that, I wasn't surprised that Bartrand wasn't able to fully utilize the powers of the idol, and Meredith was able to utilize more of it.
Maria Caliban wrote...
Magic should make something move not because it has joints but because it resembles something that can move.
Scarecrows, gingerbread men, dolls, puppets, statues, wood carvings of animals/people, snowmen - all things that wouldn't necessarily have joints but could easily spring to life.
Did the dwarven golems have joints? They look kind of jointy.