Aye, they should really indicate whether they are balanced or not, as it's obviously going to be a concern. I had a look around and whilst most people agree they aren't balanced, there's no definite answer.
(I did find a few other sets, they all look pretty cool)
I'm inclined to agree with Stella that they are meant as a display item seeing as they come unpainted.
Or maybe the company didn't think ahead
Really, without them saying something one way or the other, we won't be able to work it out ;)