I don't disagree, Mike, but privacy screens are not load bearing (normally) and that's a lot of extra trouble to go to for no specific gain. As I say, prepainting the stock before assembly sort of accomplishes the same thing in sealing out moisture...as long as you don't machine it after it's painted! My other point was that by doing 1/2 laps and/or dadoes it effectively reduces the front to back depth. In most cases that's counter productive in reducing the through visibility from an angle; the point of a privacy screen.
I've got exactly that problem now, trying to cut down the sightline to our hottub from the neighbors' yards. I may even go to 4 layers of 1" material, staggered. Needless to say, a mockup before I commit to that much time and material...