I worked for a wood protection company for several years as Product Development Manager, and we did lots of testing on "waterproofing" formulations. Of the commercial products, Thompson's was one of the poorest performers as far as protecting the wood from moisture absorption, but it beaded well on the surface. Apparently that was enough to let them dominate the market, just because it looked good when you poured water on it, and even though it needed to be reapplied every six months. Go figure.