Does it have enough wits to care? I don't recall it doing anything but appearing out of nowhere and kicking the gate in. It might be a true one-hit wonder.
It's about as realistic as the giants themselves or the way the giants are fought. After all, this wouldn't be nearly as exciting a show if they did the obvious thing and developed splendid artillery and mines that would make short work of the giants, when employed with intelligent tactics and general strategy. Better have young people swinging around using cables and swords instead!