Just how "wet" the place was is a matter of perspective.

Relative to bodies like the Moon, the amount of water that paper is talking about is of course huge -- it argues that aqueous processes were important, though not dominant, in shaping parts of Mars.

But that "not dominant" is important. One of the more thought-provoking comments I've heard was by Alan Howard, who's been studying the morphology of all sorts of Mars features, and concluded that the grand total of erosion during the Noachian was comparable to 1 to 10 million years in the U.S. Great Basin -- Nevada, Utah, etc.

That amount of water is plenty of erode landforms and alter minerals, and again, means you really can't ignore water in the early history of Mars.

On the other hand, 1 to 10 million years spread over half a billion years gives you a Noachian that is 1/50 to 1/500 as "wet" as modern Nevada. And that was the rainy season! The difference between "Death Valley" and "dessicated" is really really huge in the planetary scheme of things, but neither look terribly damp by human / Earth standards.