There is that, but think about it, it's easy to populate a small site with some pages of typing.
It takes very little in terms of character/word strings to generate a fully unique signature, really just a few sentences is all you need. And if you write those on your own, out of your own brain, they almost have to be unique.
I think that may be it in parts anyway.
I know we hit the main bump after a foolish addition of roughly duplicated content that roughly doubled the site's main content pages over a month period after fairly long period of relative low activity, what exactly was going through client's mind when he had that done is totally beyond me, he's a very smart guy, but this was a huge slip.