The "liquid water films" these folks are talking about are only one or two molecules thick. They are fleeting and ephemeral. The evaporate being discussed here is the product of millions of years of dust interaction with the very minute amounts of water in the amosphere. Keep in mind that the martian atmosphere, on average, is about 10,000 times drier than the atmosphere of earth. And if Sinus Meridiani is "above average" what does that tell you about conditions on the rest of the planet?

So the answer is "no" don't expect to be making a practical working solar still on Mars anytime soon.