There would be no significat reason to use more than three pins (as all mono XLR have).
One for minus, one for ground, and one for sound (+).
I believe that it was used just the same way as (for example) some guitarists would use stereo 6.3mm (1/4inch) cable for their signal. In principle yes, they are getting "better" signal because the resistance of one pin of the cable is somewhat lower.. But then again - a good cable will have a really low resistance (impedance) to begin with.
To sum up, there is no advantage except for one thing - in theory it is possible that such a cable could be used for longer distances. (Perhaps that's why they are sometimes being used?) But anyone would be better off to use the appropriate tools for longer distances.