ferment dry?

It means to ferment until a hydrometer reads a low S.G. Usually under

"Dry" is an oenophile ... uh that's wine-lover ... term. It means the wine is not sweet. Don't worry, a "dry wine" is still "fluid". Pours out of bottle into glass, and you can swallow it without having something to wash it down with. :)

Either the flavors in the wine recipe in question won't taste right with residual sweetness, or the alcohol/flavor balance is more suited to a dinner wine (who want's a sweet wine with their pot roast?).

Or maybe the author is worried you won't be able to figure out how to stabilize a sweet wine, and doesn't want the liability of shattered glass wine bottles.