Do you have data to back that claim up? I remember reading evidence to the contrary, namely that programmers working on the same problem -- even in different environments -- tend to produce roughly the same set of bugs.
The conclusion of that study was that parallel development mainly accomplishes a false sense of security, and most of the additional reliability in those projects came from other sound engineering techniques. But I have lost the reference, so I don't know how much credibility to lend my memory.
