Isn't that just another filter for luck? You're filtering out candidates who don't know about the meetup, or have kids and can't make the meetup's evening hours, or prefer another meetup that happens to be at the same time elsewhere, etc.
However, he apparently has no shortage of suitable talent available when using this method.
The problem, of course, is that the odds are good he's hiring people who are less skilled than some people he's filtered out. In a perfect market his product would get beaten by whoever hired those better candidates he ignored, but we live in an incredibly imperfect market and it probably won't make a difference.