He's talking about doing it as a means of adding additional zinc as a nutrient for the yeast. Earlier in the article he seems to indicate that a low level of zinc is mainly a problem for extract brewers.
I imagine its the same as using yeast hull nutrient. I've been thinking about adding some to my beers ever since I brewed my mini-mead. All my beers take two weeks to ferment. Maybe the zinc level is my problem since I am brewing with extracts. I'll try adding a little to my next batch to see if it helps out.
Planning: Agave Witbock, Raisin Beer
Primary: GF Hazelnut Stout
Tertiary: Cranberry-Pom pLambic (est. bottle date: 03/01/08)
Drinking: Cab.Sav/Merlot Wine, Grand Cru, Hazelnut Stout #3, Ordinary Bitter