I use something very similar on my folding bike. But instead of buying it from Amazon I cut up an old 1 liter soda bottle and strapped it to the downtube. The main advantage is that the surface facing the tire is fully concave and therefore the spray bouncing off of it is directed down and inward instead of outward as it would be upon hitting the convex surface of the downtube. The SKS product looks like it has a surface that's partly concave and partly convex so I wouldn't expect it to work as well as my soda bottle remnant (which also has the advantage that the cost was just the loss of the 10 cent deposit).

My makeshift front fender does help keep my feet a little drier but not as effectively as a full fender would. OTOH, a full fender makes the bike harder to pack into my suitcase for air travel.