Equally you could point to numerous systems not developed using any form of peer review and conclude the opposite. In the matter of fact there's probably more bad systems hacked together by solo programmers than there are written by communicative teams.
Systems that have no review of any kind are normally the ones that fail. Whether you are pairing or submitting to opensource where your code is checked, the quality goes up because things are checked.
The more effective the communication the better the software. If two teams don't work well together, that is reflected in the software.
