Interestingly enough, the DIR guys have been doing specimen and sample collection for years with their configuration, so to say it doesn't work is a little disingenuous. And unless your IDC friend is a member of the WKPP, I'd be hard pressed to believe that his specimen collection has been done under quite the same rigorous conditions.
Not to mention that part of the DIR philosophy, as I understand it, is to use what's needed to get the job done and not use what's not needed. DIR-minded people would have no objection to adding some special item of gear to the standard configuration if it is truly needed to accomplish some particular goal. However, I suspect that DIR-minded people could come up with something to aid sample collection that doesn't involve extra D-rings.