I saw that as more of a technicality than a demonstration of his power. The source of the bodies were from his DNA, thus it was not a big deal that he could easily break it. Though it does severely complicate things for Orochimaru. I guess they are 'lucky' that it's the 1st that can do that rather than anyone else because the 1st is the only one benevolent enough to put up with their bullshit.