Mark, I've read this online, too. And I've always ignored this advice.
The online wisdom is that disturbing the sump plug can cause dirt to come loose and block oil passages, possibly causing a malfunction.
I've always removed the plug as a regular part of the oil-change process. It lets any dirty oil drain out of the sump and also gives me a chance to clean the screen and inspect for any traces of metal or other gunk that could be an indication of a future problem.
More importantly, the bike's original manual says to do this.
-- Peter